Performance Acoustics: The Importance of Diffusing Surfaces 3118 (B-2)and the Variable Acoustics Modular Performance She!I--VAMPS TM

4A/B-2Peter D'AntonioRPG Diffusor Systems, Inc.Largo, MD 20772, USA

Presented at Auo,othe 91st Convention1991October 4-8New York

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AN AUDIO ENGINEERING SOCIETY PREPRINT

PERFORMANCE ACOUSTICS: THE IMPORTANCE OF DIFFUSING SURFACES ANDTHE VARIABLE ACOUSTICS MODULAR PERFORMANCE SHELL-VAMPS TM

Peter D'AntonioRPG Diffusor Systems, Inc.

12003 Wimbleton StreetLargo, MD 20772

ABSTRACT

There has been significant research in stage acoustics within the last decade. This research is focusedon determining the appropriate distance, disposition .and composition of sound scattering surfaces on thestage enclosure. The acoustical design of stage enclosures must try to satisfy the sometimes contradictoryrequirements for solo performance, chamber group, full orchestral and chorus as well as providingsufficient sound projection into the hall. Since the introduction of the QRD in 1983, there has been anexpectation that, in addition to improving critical listening spaces, these new surfaces would enhance theacoustics of stage and pit performance environments. The case studies presented in this paper are partof an ongoing research program to satisfy these expectations and develop a new generation performanceacoustical shell. This goal has been realized in the evolution of a variable acoustics modular performanceshell called VAMPS TM.

[1] INTRODUCTIONDuring solo, band, chamber, orchestral or choral performances there is a need for surfaces or enclosures,conventionally called acoustical shells, which surround musicians. The acoustical shell reinforces andblends the sound projected toward the audience and also heightens the ability of the musicians to hearthemselves and as well as other musicians in the ensemble. Acoustical shells typically incorporate a rearwall, flared side walls and a projecting canopy which are all structurally supported with either acounterweight or leg mechanism. In addition to the orientation of the shell surfaces with respect to theperformers, the nature of the acoustical surfaces is critical to good performance. A shell can containreflecting surfaces, which re-direct sound, diffusing surfaces which uniformly distribute sound, andabsorbing surfaces, which attenuate sound. The temporal and spatial response of these acoustical surfacesis shown in Fig. 1. The object of our stage acoustics research, which involves objective measures as wellas musician's perceptual evaluations, is to determine the appropriate combination and orientation ofreflecting, diffusing and absorbing surfaces to optimize performance. The results of this investigation willbe presented in case studies which describe the purpose and conclusions from each experiment. Adescription of the patent pending variable acoustics modular performance system will then be given.

[2] FACTORS AFFECTING ENSEMBLEEarly reflections among musicians greatly improve their sensation of playing as a group if the reflectionsoccur within a temporal window which is dependent on the nature of the musical program material,typically between 17 ms and 35 ms; include high frequency content roughly between 500 Hz and 2000Hz, containing the attack transients which are cues for rhythm and expression; contain a balance of allthe parts in the ensemble at all performance positions [1]. The first condition is easily met by spacingthe shell an appropriate distance from the performers, while the second and third requirements dependon the nature of the shell surfaces themselves. Prior acoustical shells have used flat reflecting panels andvarious forms of surface irregularity, such as curved surfaces, polycylindrical and fluted columns, etc.,

to provide sound diffusion. Despite the usefulness of these partially diffuse forms of relief ornamentation,experimental measurements and observations [2,3] reveal limitations in either the uniformity of thespatial response, the degree of independence from the direction of incident sound, the diffusionbandwidth, the temporal density, or the frequency response. We were interested in developing a newgeneration acoustical shell that uses a unique sound diffusing surface based on mathematical numbertheory sequences. This surface is called a reflection phase grating (RPG TM) and provides optimal surfaceirregularity for broad-bandwidth wide-angle scattering [2-50]. The RPG provides diffuse reflectionscovering the essential part of the spectrum to aid ensemble, and because of the uniform wide-anglescattering properties, a well balanced reflection pattern is provided for all performers. This blending anduniform distribution of the sounds from each member of the ensemble to all performers is illustrated inFig. 2.

Each point on a reflecting surface, whether flat or diffusive, can be considered as the source of aspherical wave. When the surface is flat, destructive interference between all these point emitters occursin all directions except the specular direction. That is, all energy components in non-specular directionscancel each other. Even though all points on a specular surface are contributing to the scattering process,it is useful to consider a specular reflection as arriving from one point on the boundary which satisfiesthe condition that the angle of incidence equals the angle of reflection. Consider the indirect energyarriving at an observation point from three sources (dots), and a boundary surface shown in Fig. 2. InFig. 2a it can be seen that each source is reflected (dotted lines) from only one point, on the specularboundary surface, to the observation point (O). If one or more of these boundary positions is absent ornon-reflective, the indirect energy from that source will not reach the observation point. Each observationposition receives indirect reflected energy from the three sound sources from different positions on thespecular surface. If the specular surface is replaced with an array of RPGs, vertical dashes Fig. 2b, eachdiffusor element on the surface has a scattering component (dotted lines) in the direction of theobservation position (O), from all sources. This leads to uniform coverage in that all sources arescattered to all observation positions, from all elements on the RPG surface. The difference betweena specular surface and an array of RPGs, is that each element on the diffusive surface, instead of onlyone, has a component in the direction of the observation position from all sources, instead of only one.

To illustrate this fact the sound scattered from a purely reflective and diffusive shell was measured. Thiswas accomplished by placing a loudspeaker/microphone combination in front of each shell. Using aTechron System 12 acoustical analyzer the direct swept sine wave chirp test signal from the loudspeakerand scattered energy from the shell are measured and displayed in an energy versus time display. Thespeaker was placed approximately 3' in front of the shell and the microphone was placed 18" awaytoward the shell and 3" down. In Fig. 3a the direct and reflected sound detected by the microphone infront of a purely reflective shell is shown. The full scale intense reflection at 1.3 ms is the direct soundand the two isolated reflections at 8.4 ms and 11.0 ms are the strongest reflections from the shell.Fig. 3b illustrates the diffuse reflection pattern recorded by the loudspeaker/microphone combination infront of a diffusive shell consisting of lower lateral diffusors and upper vertical diffusors. Again thedirect sound occurs at 1.3 ms, but now instead of a few sparse reflections, a rich diffuse sound fieldbeginning at 8.5 ms and extending over a significant period of time is recorded. This measurementdocuments that the sounds from all performers are scattered from all elements on the RPG surface toall performers.

There are three types of QRD diffusing surfaces which can be used in performance shells, l-dimensional (I_D), 2~dimensional (2-D) and fractal QRD diffusors are shown in Fig. 4. The 1-D QRD,

Fig. 4a, consists of a linear periodic grouping of an array of wells of equal width, but different depths,separated by thin dividers. The 2-D diffusor based on a quadratic residue sequences is called anOmniffusor TM, Fig. 4c, and consists of a 2-D array of square, rectangular or circular wells of varyingdepths, separated by thin dividers. The Omniffusor possesses two vertical mirror planes of symmetry andfour-fold rotational symmetry. This symmetry insures that the backscattering is identical in both thehorizontal and vertical planes. A schematic comparison between the hemidisk coverage pattern of a 1-Ddiffusor and the hemispherical coverage pattern of a 2-D Omniffusor are shown in Fig. 5. In Fig. 5a theincident plane wave is indicated with arrows arriving at 45 o with respect to the surface normal. Theradiating arrows touching the hemidisk envelope indicate the diffraction directions. In Fig. 5b theincident plane wave is indicated with arrows arriving at 450 with respect to the surface normal. Thearrows radiating from the hemisphere envelope indicate a few of the many diffraction directions. Thefractal diffusor, which is called a Dlffractal TM, Fig. 4b, is essentially a multi-way crossed over diffusingsurface, designed much like a loudspeaker, which consists of nested diffusors each covering a specificbandwidth. Since these surfaces tend to be large when extending to low frequencies, they are moresuitable for fixed acoustical shells. In the present investigation we report only on the 1-D QRD.

[2] PERFORMANCE CASE STUDIES

Study: I [IMay 1986Case

Venue: The Opera House, Boston, MA

Analysis: Pit Rail Reflection Analysis

Experiment: The pit rail was covered with three materials- Velour Curtains, WoodenPanels and RPG Diffusors

Response: Musicians within 20' overwhelmingly were in favor of the RPGs. Beyond20' ability to perceive difference was evenly divided.

Comments: "The playing space seemed to be larger""I could bear the rest of the orcheslxa much better""I heard the strings for the first time (Timpanist)"

Result: RI:'Gs remained in place for the entire run of Tosea and plans forpermanent installation are in progress.

Collaborators: Gary Harris, Sarah Caldwell and The Opera Company

Case Study: 2 April 1987

Venue: Wolf Trap Farm Park, Vienna, VA

Analysis: Pit Rail and Sectional Partition Analysis

Experiment: RIK]s were placed on the pit rail, between percussion and woodwinds,behind the brass and between brass and strings, Fig. 6.

Response: Musicians responded favorably to the Biffusor partitions. RPGs improvedstring blend and sense of ensemble.

Comments: "The acoustic orchestral blend improved in the house (House Manager)"Result: Musicians requested RPGs remain in place for the Tales of Hoffmann

performances.

Collaborators: Farrell Becker

IICase Study: 3 Il July 1987

Venue: Circle Theatre, Indianapolis, 1N

Analysis: Stage Acoustics Analysis

Experiment: Rl_s were used as performance partitions and on upstage wall, Fig. 7.

Response: 1. RPGs replaced plastic reflective panel traditionally used in front of brassand percussion. The RPGs gave considerable relief without specularityeffects.2. The trumpet and trombone players preferred the return when the RPGswere tilted 45 degrees to the floor.

Comments: "The RPGs improved the balance and quality of the ensemble as heard inthe hall"- Don Davis

Result: This research paved the way for the development of the Biffusor, a twosided abffusive/diffusive variable acoustics panel, and the Triffusor, a threesided absorptive/reflective/diffusive variable acoustics panel.

Collaborators: Chris Jaffe, Jaffe Acoustics; Don and Carolyn Davis, Syn-Aud-Con

IICase Study: 4 II December 1988

Venue: Wortham Theatre, Houston, TX

Analysis: Pit Acoustics Analysis

Experiment: The experiment attempted to improve cross-pit hearing and the conductor'sability to hear all sections of the ensemble.

Response: 1. Mounting 2'x2' RPGs on the inner pit rail with vertical wells improvedhearing throughout the pit2. The RPGs smooth out the sound of the upper strings.3. When RPGs were used with horizontal wells on the pit rail,communication between the stage singer and pit musicians improved.

Result: The Houston Grand Opera is employing the RPG Diffusor System.Collaborators: laffe Acoustics

I Case Study: 5 I April 1989- Present4

Venue: Meyerhoff Symphony Hall, Baltimore, MD

Analysis: Symphoni c Recordings with Telarc International

Experiment: RPGs were used to optimize the Green Room as a control room and alsoplaced around the perimeter of the stage in increasing numbers over theyears to improve the musicians ensemble and enhance the recordings. Thechronology of RPG application is:1. First control room use in April 1989 for the Schumann Symphonies No.2 and 3.2. Control room use and first modest stage application in June 1989 for theElgar Enigma Variations.3. Control room and stage use for the Schumann Symphonies No. 1 and 4.4. Control room and stage use for Tchaikovsky Symphony No. 4 andRomeo and Juliet in November 1989.5. Special acknowledgement for control room and enhanced stage use forthe Tchaikovsky/Rachmaninoff recording in January 1990.6. 1st use as Telarc'c exclusive acoustical system for control room andstage use for the Berlioz Symphonic Fantastique in November 1990.7. 1st use of full stage VAMPS shell, withspecial thanks for theStravinsky March 1991 recording of the Firebird and Petrushka, Fig. 8.

Response: 1. The musicians express an enhanced ability to hear themselves as well asother musicians in the orchestra2. The conductor expresses a level of accuracy, clarity and detail notpresent before diffusors3. The recorded blend, string size, spaciousness and depth of imagingwere improved4. Harshness of brass has been minimized and woodwinds can now hearthe outer strings

Result: The Meyerhoff installed a full stage diffusor shell around the perimeter ofthe stage for a one year evaluation period and uses them for all recordings,performances and rehearsals. The RPG Diffusor System has been adoptedas the exclusive acoustical system of Telarc, International to be used in allfield recordings and in-house editing. A field application of the diffusors isshown in Fig. 9 at the Dobris Mansion in Prague, the site of the TelareMozart series with Sir Charles Mackerras and the Prague ChamberOrchestra.

Collaborators: Jack Renner and Mike Bishop, Telarc International; George Alexsovitch,Meyerhoff Symphony Hall; David Zinman and The Baltimore SymphonyOrchestra.

Study: 6 11September 1989Case

Venue: Carnegie Hall, New York

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Analysis: Reflections from the rear of the hall

Experiment: RPGs were placed on rear wall of the hall to control slap echo. Objectiveand subjective measurements were conducted.

Response: Objective and subjective measures indicated the diffusors solved theproblem.

Result: RPGs were permanently architecturally integrated into the rear wall atCarnegie Hall.

Collaborators: Kirkegaard & Associates.

II

Case Study: 7 IlOctober 1989-PresentVenue: Troy Music Hall, Troy, New York

Analysis: Symphonic Recordings

Experiment: RPGs were used on stage for chamber and solo recorded performances.Andrew Rangell Beethoven piano sonatas January 1990.

Response: Dorian is using RPGs at Troy and location recordings, in particular theZurich sessions of Jean Guillou's series of Bach organ works. Anapplication can be seen in Fig. 10.

Result: Dorian is employing RPGs in all of their recording projects.Comments: "The results from the Zurich session are nothing short of incredible"-Craig

Dory.

Collaborators: Craig Dory, Dorian.

Case Study: 8 October 7-8, 1989

Venue: Cleveland Institute of Music, Knlas Hall

Analysis: Development of a new generation acoustical shell with diffusive andreflective components

Experiment: This analysis attempted to determine:1. The appropriate orientation of diffusive surfaces and the percentage ofdiffusive and reflective surfaces in a performance shell in terms of mutualhearing and projected sound quality2. The appropriate shell distance from the performers3. Two siring quartets, a brass quintet and horn duo were used4. Five different microphone systems were used for each playingenvironment to obtain 5 simultaneous DAT recordings:a. The Head Acoustics mannequin, with microphones at the entrance to theear canal, was placed within the group to determine ensemble blendwithout self maskingb. Etymotic Research probe microphones, Fig. 11, were inserted into theear canal to determine ensemble blend with self maskingc. Helmuth Kolbe's headband microphones, located at the entrance to theear canal, were used to monitor ensemble blend with self maskingd. An omnidirect[onal microphone was placed within the group as amonophonic controle. Spaced omnidirectional microphones were placed in the front of thehouse to measure the projected sound quality5. Recording Equipment: 5 Panasonic 3500 DAT recorders6. The RPG shell consisted of (8) 4'x4' QRD modules with specular backpanels arranged to form a barrier behind the musicians 16'(W)x8'(H).

Response: String Quartet (Fig. 12-14):1. The string ensemble preferred a mixed orientation shell with lowervertical wells and upper horizontal wells. Some musicians preferredspecular support on the lower surfaces for better bass coupling.2. Mutual and self hearing was unanimously improved3. The general reaction was that the diffusive shell provides warmth andintimacy and minimizes harshness4. The preferred shell distance for warmth and intimacy was approximately3-6'5. The preferred shell distance for projected sound quality was 9-12'6. There was unanimous agreement that a height of 8' was better than 4'

Brass Quintet (Fig. 15):l. The brass quintet preferred a mixed orientation shell with lower verticalwells and upper horizontal wells2. The brass experienced harshness from a completely reflective shell anddid not prefer upper diffusors with vertical wells3. The preferred distance for mutual and self hearing as well as projectedsound quality was 9'.4. A horn duo preferred a mixed diffusive and specular shell atapproximately 6'

Result: The musician's positive response and enthusiasm encouraged thedevelopment of a new generation performance shell which incorporateddiffusion

Collaborators: Tom Knab, CIM staff and students; Jack Rennet, Telarc; Wade Bray, JaffeAcoustics; Dana Kirkegaard, Kirkegaard & Associates; Tech support fromMead Killion, Don and Carolyn Davis, Dave Andrews and Joseph McGee,Fig. 16.

Careful audition of the DAT recordings and listener preferences led to the development of a newacoustical shell incorporating a lower reflective section below the listeners ears, vertical 1-D Diffusorsproviding horizontal diffusion at ear height and 1-D horizontal diffusors above ear height providingdiffusion in the vertical plane. Because the size of the performance group, disposition on stage, programmaterial, conductor's preferences, etc. are variable, it was decided to design a portable variable acousticsmodular performance shell which incorporate the concepts of reflection, diffusion, absorption, variabilityand a reflecting cantilever. This concept is called VAMPS.

To evaluate this new performance shell design musicians in a string quartet and brass quintet (CaseStudy 9) were asked to respond to eight perceptual questions on a scale of O-unacceptable, 1-poor, 2-fair,3-good and 4-excellent. A perfect score being 32.

CaseStady:0IIMarch23-24,1991Venue: Cleveland Institute of Music, Kulas Hall

Analysis: Evaluation of the new VAMPS acoustical shell

Experiment: The shell was placed at a preferred distance of 6' for the string quartet and9' for the brass quintet. The shell consisted of a lower row of (8) 2'x2'reflective panels, an intermediate row of 8 vertical 2'x2' diffusors, anupper row of (8) 2'x2' horizontal diffusors and a reflective cantileveroriented at 45 . The shell was configured in a diffusive/reflective format,Fig. 17, completely reflective format, Fig. 18, and for comparison, thestage curtains were also used as a control, Fig. 19.

Response: The respondents scores are listed in Fig. 20-21. Fig. 20 tabulates theindividual perceptions to the eight questions for the string quartet. Asummary of the preferences for the three environments is shown at theupper right. VAMPS is the preferred shell. Fig. 21 tabulates the individualperceptions to the eight questions for the brass quintet. A summary of thepreferences for the three environments is shown at the lower right.VAMPS is the preferred shell.

Result: The VAMPS concept has moved into production

Collaborators: Tom Knab, CIM staff and students; Jack Renner, Telarc

Enthusiastic response from the BSO musicians and conductor during Telarc sessions led to an objective

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measurement of the stage acoustics and subsequently an subjective official evaluation of a full stagediffusive shell system reported in Case Study 10.

Case Study: 10 "1 April 25, 1991

Venue: Meyerhoff Symphony Hall

Analysis: Evaluation of the new VAMPS acoustical shell. Musicians were asked toresponds to 6 questions on a scale of 1-4 without and with the diffusiveshell. The questions were: rate the ability to play in rhythmicsynchronicity, intonation perception, ease of tone production, ability tohear distant instruments, ability to mutually hear instruments in adjacentsections, and ability to hear your own instrument. A perfect score is 24.

Experiment: The shell was placed around the perimeter of the stage, usingapproximately (22) 4'x12'x9 1/8" sections. The shell consisted of a loweropen support which allowed sound to reflect from the hard existing wallbehind the shell. The next 2' high tier consisted of horizontally diffusingdiffusors with the center of this level at seated ear height. The next 4' inheight contained all vertical diffusion. A 24" cantilevered plexiglasscanopy was oriented atop the vertically diffusing QRDs at an angle of 45 owith respect to the face of the diffusors.

Response: The purpose of the experiment was to blend the outer strings into thewoodwinds, decrease the harshness of the brass, intensify the fullness andwarmth of the strings and enhance the sense of ensemble and rhythmicperformance of the musiciar_s.

Result: The shell was extremely well received and plans for a permanentinstallation are under way. This same arrangement was also used for thehighly acclaimed Telarc recording of Stravinsky's Firebird and PetrushkaCD-80270. Musician's preferences are listed in Fig. 22-24. Fig. 22tabulates and plots the Baltimore Symphony Orchestra's average sectionalevaluation of the existing stage. Fig. 23 lists and plots the BSO'sevaluation of the full stage QRD shell. Fig. 24 illustrates the general levelof satisfaction the BSO experienced in using the QRD shell. The averagepercentage improvement was 83%, with a high of 144% and a low of 42%.

Collaborators: BSO musicians and staff and RPG.

The following are a summary of section comments from the musicians which accompanied theperception questionnaire.

ViolinMuch, much better with RPGs.

ViolaThe woodwinds and basses are clearer with the RPGs. Brass are even louder than before. There is a

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basic improvement in most areas, but the synchronicity between 1st violin and viola remains a majorproblem. With the public it felt less reverberant, a little dead. With the RPGs we can hear the real soundof the 1st violins instead of the echo. Also from the back we can hear the viola section for the 1st time.With the RPGs the Cello sound is so much more focused and the winds sound like a unit. Its easier tohear the violins. Quality with RPGs is somewhat bright and raw. I don't like the way my instrumentsounds with the RPGs. Its very raw and scratchy with no bass overtones. It reminds me of Salisbury.It takes more effort to play even though the ensemble improves. Congratulations! I love the diffusors.Sound is much warmer. Tendency to force sound is reduced. Brass not as overpowering. Ensemble mucheasier, reverb got in the way before. Easier to hear all around. Rhythmic underpinnings are more present,no longer buried by acoustics.

CelloWinds especially have much richer, integrated sound. I'm very encouraged by the potential in theseRPGs to make this a great hall. For the first time I can hear the timpani's beat. I feel my intonationshould improve at rehearsals and concerts because I can hear myself. In the past it Was worse after arehearsal because I couldn't hear myself. Also the brass doesn't hurt ones ears the way it did whensitting close.

BassThe effect is better without the plastie on the rear diffusors. Cellos are better and the bass is moreintegrated.

FluteWith RPGs I don't have to push sound to be heard. The RPGs are a definite improvement.

OboeThe RPGs are at their most valuable in cutting down superfluous sound on stage. Tone color seems alittle darker, much fuller and more focused with RPGs. Bass was more even and not boomy with RPGs.Significant impact on basses. RPGs offered more clarity and warmth.

Clarinetwithout the RPGs the sound has too much treble and sounds too thin; My instrument feels like it hastoo litde resistance. It is also difficult to play soft without the RPGs. With the RPGs I can hear myselfbetter and the sound is deeper, more bas and has more core. However, for me it lacks a little brilliance.

BassoonMy tone blends better and the piano sounds meatier. The brass were more controlled. Generally, somebrightness was eliminated. Without RPG I like my sound better when playing alone on stage, but I likeit better when the orchestra is playing with the RPGs. I would like to try risers.

HornI can understand the conductor with the RPGs. The biggest improvement is the ensemble. This is a realproblem with the BSO, but it also has been a convenient excuse to justify bad playing. For the fa'st timein 9 years, I hear difference tone beats. I can hear the conductor talk. The general clarity of the orchestrais improved. I didn't give mo m 4s only because I hope further improvements will be possible. I like theRPGs.

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TrumpetI play louder without the R./_s. The stage sounds more resonant, but muddier without the RPGs, thusI cannot hear various instrument groups without RPGs. I cannot hear the violins in real time. I hear alater reflected sound and so to play with the strings I must play ahead of them. With the Rt_s I feelthat I can play with different tone colors, more colors and more control. I feel more confident with theRPGs.

TromboneWoodwinds and upper strings sound louder and cleaner. It has been noted the brass sounds more edgybut softer from audience, however, the benefits outweigh this problem. I preferred sound without plasticreflective cantilevers on the rear baffles. Plastic sheets seem to go too far.

TubaSound is much clearer. Intonation and proper releases are much more critical with RPGs. Feels more likeCarnegie Hall. Don't like the plastic above the rear diffusors it makes the stage noisier.

PercussionTimpani is still unclear. No clarity in rhythmic passages.

Paul BlackmoreThe strings are complete and full with good section sound. The quality of attack is similar. Brass arebetter. Don't sound like laser beams. Percussion sounds dull. Tympany attack is reduced.

David ZinmanThe sound is 100 percent better.

[3] THE VARIABLE ACOUSTIC MODULAR PERFORMANCE SHELLAll of the case studies suggested the development of a variable shell, which could include all of theingredients of the acoustical palette. The VAMPS shell which evolved utilizes a sturdy tubular metalframing system forming 2'x2' modular cells into which any absorbing, reflecting or diffusing modulescan be inserted. Two formats for the shell are possible. A 2'(H) x 10'(W) portable shell tower, Fig. 25,which can be disassembled and a 6' (W) x 12' (H) transportable and movable welded shell, with 2'x2'modular openings, hinged cantilever and counterweight support system. Each format can accept any2'x2' acoustical insert. Only the former will be described here.

The framing system forms independent or coupled towers, Fig. 26, with openings which accept modularacoustical inserts. The towers are self-supporting and when linked with splayed side sections, typicallyangled at 120, form a very stable lattice framework which can accommodate a wide range of acousticalsurfaces. The uppermost section of the shell is an angled (typically 45 o) reflective canopy which projectssound toward the audience. VAMPS can be conceptually thought of as a tubular framing system whichis divided into a modular reflecting lower section, a diffusive middle section and an upper reflectivecantilevered canopy. Fig. 27 shows the Cavani String Quartet performing with VAMPS at the ClevelandInstitute of Music. Another performance at the Kohl Mansion in Burlingame, CA is pictured in Fig. 28.

[3.1] Aluminum Framing SystemThe aluminum framing system consists of 15/16" or 1" square aluminum extrusions and 2-, 3-, 4-, 5-,and 6-sided injection moulded nylon connectors. Three sided connectors at the base can accept casters

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for mobility. The aluminum tubing can either be simply press-fit over the connectors or press-fit overself-locking spring plungers imbedded into the connectors. Insertion of the plunger into a hole in thealuminum tubing provides a positive lock. Towers can either be independent providing easy mobility oreconomically coupled to adjacent units for semi-permanent setup. An isolated tower consisting of 4nominal 2'x2' modular openings requires (4) 3-sided connectors at the top, (4) 3-sided connectors withcaster inserts at the base, (12) 4-way connectors for the additional three horizontal square sections and(36) 24 3/8" sections of aluminum tubing. Towers can be interconnected by using (2) 4-sided connectorsat the top and bottom and (6) 5-sided connectors in the three internal horizontal sections on one side.Thus coupled towers eliminate the need for (10) connectors and (13) 24 3/8" aluminum sections.

Individual towers can be rolled about freely or tilted backward to allow transport through doorways.Coupled towers can be rolled within a space for optimum positioning. Rear and splayed (typically 120))side wall framing sections are connected with a stabilizing mechanism which maintains the angle. Fortransport or storage the aluminum framing system can be completely disassembled or partiallydisassembled into square of rectangular sub-sections, which afford quicker re-assembly.

[3.1.1] Mounting "T" Face FrameThe acoustical modules are attached to the aluminum framing system via a stained or painted hardwood"T" face frame, Fig. 50, which is permanently connected to the acoustical element. The lower sectionof the "T" frame is molded to form a square groove which straddles the square aluminum framing thussecuring it in place. The "T" frame press fits into the aluminum opening and is secured in place via avariety of locking mechanisms including, but not limited to, friction, a rotating lever, spring loaded bailplunger, etc.

[3.2] Lower Reflecting SectionFor the soloist and orchestral ensemble, the lower section consists of one 2'x2' reflector to elevate andposition the diffusor at ear height. For choral performance, with a riser whose last row may be as highas 45" above the ground, the shell contains two or more reflecting sections to elevate the diffusivesection to ear height of the rear chorister. The lower reflective panels provide half space bass support.

[3.3] Mid Diffusor SectionThe diffusive section contains two or more diffusor modules. The lower 1-D horizontal diffusors withvertical wells scatter sound laterally across the stage. The upper 1-D vertical diffusors with horizontalwells, scatter sound which would normally rise and be reflected by a flat surface into the reverberantfield, back down into the performance area as well as into the canopy. If 2-D diffusors are used, thenboth panels are similar since 2-D omniffusors are hemispherically omnidirectional.

[3.4] Upper CanopyThe upper cantilevered canopy serves several functions. It projects sound from the rear of the stageforward; reflects sound coming backward from the front of the stage downward to the rear performersections; and reflects diffuse sound from file upper vertically diffusing section forward.

[3.4.1] Canopy Mounting "T" Face FrameThe uppermost section of the shell is a reflective canopy which'is bolted to the aluminum framing. Thecanopy "T" frame is either rectangular for adjacent linear segments or trapezoidal to allow adjacentsections to be mounted at an angle of typically 120. Thc base of the canopy "T" frame is moulded witha square groove appropriately angled to allow the canopy to project forward of the face of the shell by

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450.

[3.5] Angled Side ConnectorsThe splayed side sections are attached to the rear section with connectors which straddle the aluminumframing and provide the appropriate angle. The light gap between adjacent towers forming the side-rearintersection is concealed with vertical black inserts tapered at the appropriate angle and incorporatingthumb holes for easy insertion and removal. Two horizontal angular spacers and one vertical spacer isrequired for each vertical 2'x2' modular opening.

[3.61 Acoustical Insert ElementsThe modular acoustical surfaces can include:Abffusor - broad-bandwidth absorber which simultaneously provides sound diffusion.Absorbor- broad-bandwidth sound absorber.A!mute tM- sintered glass sound absorber. The low frequency absorption bandwidth can be tailored byvarying the air gap behind the panel.Reflector- rigid sound reflector.QRD Diffusor- broad-bandwidth wide-angle 1-dimensional sound diffusion.Omniffusor- broad-bandwidth wide-angle 2-dimensional sound diffusion.Terrace tM- broad-bandwidth wide-angle 2-dimensional sound diffusion, without cell dividers.

Fabric can also be stretched over the face frame to conceal the acoustical surface and provide a uniformset or backdrop.

[4] DISCUSSIONVAMPS utilizes a wide complement of acoustical inserts to address ensemble, projection, on-stageloudness and hearing impairment, and on-stage frequency balance.

[4.1] ProjectionIn addition to providing a heightened sense of ensemble and support the acoustical shell projects soundtoward the audience. The VAMPS shell utilizes a stiff lower reflecting section and upper reflectingcanopy to project sound. The reflecting sections are formed from either wood, particle board orlaminated paper honeycomb for a light weight and stiff non-diaphragmatic panel.

[4.2] LoudnessMusicians are becoming more sensitive to hearing impairment due to sustained loudness on stage.VAMPS lowers the impact of loudness by diffusion, which uniformly distributes the sound so that thelevel in any particular direction is diminished. In addition, the modularity allows use of low-frequencyor broad-bandwidth sound absorbing modules in the vicinity of high intensity instruments like brass andpercussion. Strategically placed absorbing panels also improve ensemble balance and allow musiciansto hear more distant softer musical sections.

[4.3] Frequency BalanceThe ability to add dedicated bass absorbers covering specific frequency ranges or broad-spectrumabsorbers provides the ability to tune the shell to the conditions on stage. Thus the frequency balanceon stage can be adjusted to a particular music ensemble_ musical piece or stage. This can beaccomplished with a new sintered aluminum sound absorbing panel whose frequency response can beadjusted by varying the depth and fiberglass contents of the rear air cavity.

13

[4.4] PortabilityVAMPS provides the performance of a fixed shell in a portable format. The aluminum framing systemeasily disassembles for pacldng and transportability and the acoustical modules stack easily. Thus thereis no sacrifice in performance for portability.

[5] FULL STAGE SYSTEMSA full stage arrangement is illustrated in Fig. 29. The ceiling canopies offer specular reflections, fromthe front curved lip to project sound into the audience and diffusion, from the underside, for enhancedensemble. For fixed stage enclosures the design offered in Fig. 30 provides significant energy to theperformers as well sound projection if the cantilever is utilized. The lower diffusor scatters soundhorizontally, while the diffusor above it scatters sound in the vertical plane. Some of this scatteredenergy is directed back towards the musicians and some of it is re-scattered towards the musicians fromthe soffit above. The vertically diffusing QRD mounted on the soffit also scatters sound back down tothe musicians as well as into the cantilever, which in turn projects the sound forward. The reflectivesoffit and the cantilever also direct sound from downstage into the diffusors for subsequent re-scattering.For fixed built-in stage shells this design may prove effective.

[6] REFERENCES:[1] A.H. Marshall, D. Gottlob and H. Alrutz, "Acoustical Conditions Preferred for Ensemble", I. Acoust.Soc. Am., Vol. 64, No. 5, pp._1437-1422 (1978)[2] P. D'Antonio and J.H. Konnert, "The Reflection Phase Grating Diffusor: Design Theory andApplication", J. Audio Eng. Soc., Vol. 32, No. 4, pp. 228-238 (April 1984).[31 P. D'Antonio and J.H. Konnert, "The Acoustical Properties of Sound Diffusing Surfaces: The Time,Frequency and Directivity Energy Response", Invited Paper B-6, 79th AES New York (October 1985),Preprint 2295.[4] M.R. Schroeder, Number Theory in Science and Communication, with Applications in Cryptography,Physics, Digital Information and Self-Similarity, Springer, Berlin, 1986.[5] Synergetic Audio Concepts Newsletter, Vol. 11, No. 2, pp. 14-17 (Winter 1984).[6] Synergetic Audio Concepts Tech Topics, Vol. 11, No. 7 (Spring 1984).[7] P. D'Antonio and J. Konnert, "The RPG Reflection Phase Grating Diffusor", Mix Magazine, Vol.8, No. 8, pp. 74-76 (August 1984).[8] P. D'Antonio and J.H. Konnert, "The RPG Reflection Phase Grating Acoustical Diffusor:Applications", 76th AES Convention, New York (October 1984), Preprint No. 2156.[9] P. D'Antonio and J.H. Konnert, "The RFZ/RPG Approach To Control Room Monitoring", 76th AESConvention, New York (October 1984), Preprint No. 2157.[10] P. D'Antonio, J.H. Konnert and F. Becker, "The RPG Reflection Phase Grating Diffusor:Experimental Measurements", 76th AES Convention, New York (October 1984), Preprint No. 2158.[11] Synergetic Audio Concepts Tech Topics, Vol. 12, No. 1 (Fall 1984).[12] P. D'Antonio and J.H. Konnert, "The Role of Reflection Phase Grating Diffusors in CriticalListening and Performing Environments", 78th AES Convention, Anaheim (May 1985), Preprint No.2255.

[13] P. D'Antonio, John Konnert and Russell E. Berger, "Control Room Design Utilizing a ReflectionFree Zone and Reflection Phase Grating Diffusors: A Case Study", 78th AES Convention, Anaheim(May 1985).[14] P. D'Antonio, "The Reflection Phase Grating Acoustical Diffusor: Diffuse It or Lose It", dbMagazine, Vol. 19. No. 5, pp. 46-49 (September/October 1985).[15] W. Baldwin, Technology: "Applied Gozinta", Forbes Magazine, pp. 152-153 (October 1985).

14

[16] P. D'Antonio and J.H. Konnert, "Recording Control Room Design Incorporating a Reflection FreeZone and Reflection Phase Grating Acoustical Diffusors", Invited Paper D2, 110th Meeting: AcousticalSociety of America, J. Acoust. Soc. Am. Suppl. 1, Vol. 78, p. S9 (November 1985).[17] I. Peterson, "Acoustic Residues", Science News, Vol. 129, No. 1, pp. 12-13 (1986).[18] P. D'Antonio and John It. Konnert, "Advanced Acoustic Design of Broadcast and RecordingFacilities", NAB Engineering Conference Proceedings, TV Multichannel Sound Session, pp. 215-224(April 1986).[19] P. D'Antonio and John H. Konnert, "The Reflection Phase Grating Acoustical Diffusor: Applicationin Critical Listening and Performing Environments", Invited Paper E4-6, 12th ICA, Toronto (July 1986).[20] P. D'Antonio, "Control Room Design Incorporating RFZ TM, LFD _" and RPG TM Diffusors", dbMagazine, pp. 47-55 (September/October 1986).[21] P. D'Antonio and W. Peterson, "Incorporating Reflection Phase Grating Diffusors in WorshipSpaces", AES Convention, Los Angeles (November 1986), Preprint No. 2364.[22] P. D'Antonio & J.H. Konnert, "New Acoustical Materials Improve Room Design", AES Convention,Los Angeles (November 1986), Preprint No. 2365.[23] P. D'Antonio and D. Eger, "T60- How Do I Measure Thee, Let Me Count The Ways", AESConvention, Los Angeles (November 1986), Preprint No. 2368.[24] P. D'Antonio and John It. Konnert, "New Acoustical Materials improve Broadcast Facility Design",Proceedings 41st Annual Broadcast Engineering Conference, pp. 399-406, National Association ofBroadcasters, Dallas (1987).[25] P. D'Antonio, "Advanced Design of Broadcast Facilities", Broadcast Engineering (July 198'7).[26] M. Wagner with D. Paoletti, "Acoustics: The RPG Diffusor", Interiors, p. 56 (July 1987).[27] D. Davis, "The LEDE Concept", Audio Magazine, pp. 48-58 (August 1987).[28] B.V. Pisha and C. Bilello, "Designing A Home Listening Room", Audio Magazine, pp. 56-63(September 1987).[29] P. D'Antonio and J.H. Konnert, "Complex Time Response Measurements Using Time DelaySpectrometry", 83rd AES Convention, New York (October 1987), Preprint No. 2542 lB-I].[30] P. D'Antonio, F.M. Becker and C. Bilello, "Sound Intensity and Interaural Cross CorrelationMeasurements Using Time Delay Spectrometl3,", 83rd AES Convention, New York (October 1987),Preprint No. 2543 lB-2].[31] B.A. Bell, G.N. Stenbakken, D.R. Flynn, D.J. Evans, E.D. Burnett, V. Nedzelnitsky and K.R.Eberhardt, "Evaluation of A Copy Prevention Method for Digital Audio Tape Systems", National Bureauof Standards, Report NBSIR 88-3725 (February 1988).[32] P. D'Antonio, "Acoustical Troubleshooting and Modification in Broadcast Facilities", NABEngineering Conference on Studio Consn'uction and Acoustics (April 1988).[33] P. D'Autonio, "Complex Time Response Measurements Using TEF: Importance of the FunctionalForm Phase Shift", Invited Paper 86th AES International Conference, Nashville (May 1988), Paper 2.C.[34] K. Yates, "A Matter of Diffusion", Stereophile, pp. 58-77, Vol. 11, No. 4 (April 1988).[35] P. D'Antonio, "Acoustical Control of Worship Spaces", Resources Magazine, pp. 223-223 (Spring1988).[36] P. D'Antonio, C. Bilello & D. Davis, "Optimizing Home Listening Rooms, Part 1", 85th AESConvention, Los Angeles (November 1988), Preprint No. 2735.[37] P. D'Antonio, "Acoustical Design of Worship Spaces", 85th AES Convention, Los Angeles(November 1988), Preprint No. 2721.[38] P. D'Antonio, "The Reflection Phase Grating Diffusor: A Five-Year Progress Report", J. Acoust.Soc. Am. Suppl. 1, Vol. 85, p. S16 (Spring 1989).

15

[39] P. D'Antonio, "Optimizing Home Listening Rooms", J. Acoust. Soc. Suppl. 1, Vol. 85, p. S101(Spring 1989).[40] F. Alton Everest, "The Master Handbook of Acoustics", Second Edition, First Printing, TAB Books,Blue Ridge Summit, PA (1989).[41] P. D'Antonio, "The RPG Diffusor: A New Architectural Acoustic Design Ingredient", ArchitectureMagazine, pp. 109-112, 137 (June 1989).[42] P. D'Antonio, "The Reflection Phase Grating Diffusor: A Five Year Progress Report", AudioEngineering Society 4th Regional Convention, Tokyo, Paper C-10 (June 1989).[43] P. D'Antonio, J. Konnert, F. Becker, and C. Bilello, "Sound Intensity and Interaural Cross-Correlation Measurements Using Time-Delay Spectrometry", J. Audio Eng. Soc., Vol. 37, No. 9, 659-673(September 1989).[44] P. D'Antonio and J. Konnert, "Complex Time-Response Measurements Using Time-DelaySpectrometry", J. Audio Eng. Soc., Vol. 37, No. 9, 674-690 (September 1989).[45] J. Konnert and P. D'Antonio, "Comments on Diffusing Surfaces in Concert Halls", J. Audio Eng.Soc., Vol. 37, No. 10, 839_844 (October 1989).]46] P. D'Antonio, 87th Audio Engineering Society Workshop on "Optimizing The ListeningEnvironment", Chairman: Dr. Peter D'Antonio, Presentations: "Tribute To Charles Bilello"; "ReflectionControl in the Listening Environment"; "The Evolution of the RFZ TM, RPG and Full Spectrum Diffusor(FSD_")"; "Optimizing An Existing Listening Room"; "Recent Experiences Using Diffusive Surfaces toImprove Mutual Hearing on Stage and in the Orchestra Pit"; "Reflection Control in Worship Spaces",New York (October 1989).[47] P. D'Antonio and N. Grant, "The RPG Low Frequency Diffusor: A Case Study at Real WorldStudios, Bath, England", 87th Audio Engineering Society Convention, Architectural Acoustics SessionL, New York (October 1989).[48] P. D'Antonio, "Employing the Complete Acoustical Palette in Teleconferencing Design", J. Acoust.Soc. Am. Suppl. 1, Vol. 89, p. S56 (Fall 1989).[49] P. D'Antonio, "The QRD DIFFRACI'AIff: A New I or 2-Dimensional Fractal Sound Diffusor",119th Meeting of the Acoustical Society of America, Penn State University (May 1990).[50] P. D'Antonio, ""The QRD DIFFRACTAL_'": A New 1 or 2_Dimensional Fractal Sound Diffusor",89 AES Convention, Los Angeles (September 1990), Preprint No. 2938.

Trademarks: RPG, QRD, ABFFUSOR, DIFFRACT/'AL, TERRACE and OMNIFFUSOR are trademarksof PPG Diffusor Systems, Inc. ALMUTE is a trademark of NDC Co., Inc.

16

ACOUSTICAL TEMPORAL SPATIALTREATMENT RESPONSE RESPONSE

0

ABS??'r!.O.N..D'RECTSOU"'O_3o , 30/ii_i::i!_iiiiiiiiii::::i::?_'_?:i_i::?:?:i::i_i_i_?:i_iTTiiii!i'.Ti511'i ..... o

SIREC__ .90 --90

REFLECTION SPECULAR _._

....... REELECTION _ '

..... ." 6dB

/ TIME (ms)

Figure 1. Illustrates how sound is distributed in time and space after interacting with an absorbing,reflecting and diffusing surface. An absorbing surface attenuates sound, a reflecting surface re-directssound and a diffusing surface uniformly distributes sound.

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Figure 3, (a) Energy versus time curve illustrating the direct and reflected sound pattern 3' in front ofa purely reflective shell. The full scale direct sound occurs at 1.3 ms and the two most intense isolatedspecular reflections occur at 8.4 ms and 11.0 ms. (b) Energy versus time curve illustrating the direct andscattered sound pattern 3' in front of a VAMPS TM shell,

II

Figure 4a. 1-D QRDDiffusor

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Figure 4b. Diffractal TM

Figure 4c. 2-D Omnifft_sor TM

Figure 4d. 2-DTerraee TM

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Figure 6. Orchestra pit diffusive acoustical treatment at Wolf Trap Farm Park, Vienna, VA.

Figure 7. (Left) Rear wall diffusive treatment and diffusor separators between brass and woodwinds atthe Circle Theatre, IN; (Right) Close up of diffusive separators between the brass and woodwinds tominimize brass harshness.

Figure 8. Experimental full stage RPG Diffusor shell at the Meyerhoff Symphony Hall, Baltimore, MD.

Figure 9. RPG Diffusor treatment used by Telarc for the Mozart series at the Dobris Mansion, Prague.

Figure 10. RPG Diffusor treatment used by Dorian Recordings on stage at Troy Savings Bank MusicHall, Troy, NY.

Figure 11. Probe microphones manufactured by Etymotic Research.

Figure 12. Probe microphones inserted into tile ear canal of 1st Violinist. Microphone is inserted to apoint just in front of the ear drum.

Figure 13. Case Study 8 string quartet I, with tile Head Acoustics anthropomorphic mannequin (Klans)at the center. RPG diffusors are oriented with vertical lower wells and horizontal upper wells.

Figure 14. Case Study 8 string quartet I1, with the Head Acoustics anthropomorphic mannequin (Klans)at the center. RDG diffusors are oriented with vertical lower wells and horizontal upper wells.

Figure 15. Case Study 8 brass quintet, with the Head Acoustics anthropomorphic mannequin (Klaus) atthe center. RPG diffusors are oriented with vertical lower wells and horizontal upper wells. The spacedomnidirectional microphones used for audience evaluation are also shown.

Figure 16. Collaborators in the Case Study 8 experiment. From left: Elizabeth D'Antonio, Wade Bray,lack Renner, Dana Kirkegaard, Tom Knab, Peter D'Antonio, Klaus and the String Quartet I.

Figure 17. Case Study 9 string quartet in front of mixed VAMPS.

Figure 18. Case Study 9 brass quintet in front of purely reflective VAMP&

Figure 19. Case Study 9 string quartet in front of stage curtain used as a control.

Acoustical Shell Evaluation: string Quartet,KulasAuditorium CIM1st Violin 32 Musician's Perception Viola Musician's Perception

perception0-4 Perception 0-4 32

[I[111 Ambhmc_ 28 .............................................. []1_ Ambiance 28 ............................... /Musician's Perception

[_ $ytw.hnmlclty 20' _ Synchronicity 20-

:t[_ To_P_oductlon 12., _ Tone Production 12.Suppo. 8 .....................0' I Self Hearing 0 [ ........

Ambiance 01i il I 3i ToA_b_uutic O

Group Pitch 1 3 Group Pitch '".-'Synchronicity I 4 !

Intonation 0 4 Intonation O , ,Tone Production 0 4 Violin I Violin H Viola Cello

Support 0 4 Support String Quartet_mb_ I 3 {_mb_Self Hearing [ Self Hearing Maximum_-32

l S_e_ _ _w Shell fl:[qqlVAMPSAcoustical Shells Acoustical ShellsPexfotme,r-Sophia Sllivos3/23/91 Performer.lcany Smlih3/23/911StViolin Comments: VAMPSBehindMuslchua16' {W)x 10'0t)'The curtain dispe,rsed thc sound too quickly. I tended to push with thu reflective shell and it was Viola Comlrmlts: 3D.3D1hunter to he.ar tho ensemble blend.Tim VAMPSru wM wltnnex enveloping sound" There is no question that tho VAMPSTM setting was far lupelior to me. The clarity nd support

of sound was wonderful to hear, and I elmscantily hear fll_ lit violin wiLhtile prominence I'd

, like. Tho reflective seatingwas second choic_ aud th* curtalu clearly was inferior.2nd Violin

Musician's Perception CelloPerception 0-4 32 ' Musician's Perception

[mTn Ambiance 28- [1_ Ambiance 28 .........................................................

[EE_ Group Pitch 24 - _ Group Pitch 24[_] Synchronicity 20-Intonation 16- {'--'7 Synchronicity 20-

[_ Tone_uction 12- _ Intonation 16-

[_]'[_ Support 8 - '"'"'"'"'"'"'" _ _ ii [x,'Xm::_Tone production 12-

Ensemble 4- '"_. _. _ [_ Support 8-I SelfHearihg 0. _ Ensemble 4.

Ambiance : l_ Self Hearing 0'Group Pitch Ambiance l

Synchronicity Group Pitch 2.5Intonation Synchronicity

Tone Production IntonationSupport Tone Production

Ensembl_ SupportSerf Hearing En_mble/

se_m_g 3.S I 2.s I 4 IAcoustical ShellPerforraer.RebeccaL Harris Acoustical Shells3/23/91 P_form_r.Klm CookZnd Vi0llll Co--tS: 3/23/91'I felt lost in spa_ with the cumdn and tho lnue.r voices (2nd violin and viola) especially felt Cello Comments:unclear, The re/lective gw,a felt *dead". It was hlud to hear other instruments and had a hard Tho support from th_ VAMPSrI''shell mad4 articulation easy to hear, the_for* easy to blend andtime producing tone, The VAMPSrtt sound was alive, warm, ambient and I heard the ftrst violin, react to what we hear, Clean, Tho curtaha provldo no support and the sound disappears behindCleally, fuh tho inner vole24 projected really welL' me.

Figure 20. Case Study 9 acoustical evaluation of VAMPS by each member of the string quartet in KulasHall, CIM. A summary comparison of the shell variations is provided at the upper right. VAMPS wasthe preferred performance environment.

Acoustical Shell Evaluation: Brass Quintet, Kulas Auditorium, CIMTrumpet 4o Musician's Perception French Hem 4o Mtulcian's Perception Tuba 32 Musician'l PerceptionP_c4p_n 0-5 Per,piton 0-5 Pe-._lxlou0-4ff[rn Ambanc4 35 ..................................................._ fill3 Ambinn_ 35 ........................................................... [ITU1 An,ba,,ca 28 ..............................................................[:::::::l OroupPkch 30 = '"'"'-'"-'-'"'"'"'--_--- _ OroupPhch 30' [:::::::1OroupPltch 24-

[::2 sp_a_.a7 25' '"'"'"'-"_i"i::::_!_ _ Sy,,c_aactty 25- [:::2] sy,_

BSO Existing Stage EvaluationSection Perception Preferences

RPG Diffuser Systems, Inc.

Musician's Perception

04t .........Perception 1-4 16 - -

Synchronicity[_]5_ Intonation[5_ Tone Production 12

[_J_q_] Distant Hearing

_ Mutual Hearing8

II Self Hearing

4

0

Synchronicity 2,5Intonation 2.8ToneProduction 1.8DistantHearing ' 1 2.3

Mutual Hearing I iiii2_1'36'532.2.'a]81}i!iScl[Hearing J 1 [1.63L2.2

Acoustical Treatment

Without RPGs4/25/91

Figure 22. Case Study 10 evaluation of the existing stage enclosure by tile Baltimore SymphonyOrchestra. Individual sectional average scores for each question are listed and plotted.

BSO RPG Diffusor EvaluationSection Perception Preferences

RPG Diffusor Systems, Inc.

Musician's Perception24

20

Perception1-4 16[_J Sy_mhronicity[_ Intonation

ToneProduction 12

[_ Distant Hearing_z_ Mutual Hearing

8II SelfHearing

SynchronicityIntonationTone ProductionDistant HearingMutual HearingSelf Hearing

Acoustical Treatment

RPGs Located Along Stage Perimeter4/25/91

Figure 23. Case Study I0 evaluation of the fnI1 stage RPG Diffitsor shell by the Baltimore SymphonyOrchestra. Individual sectional average scores for each question m'e listed and plotted.

BSO RPG Diffusor EvaluationAverage Preferences and % Improvement

RPG Diffusor Systems, Inc.

Musician's Perception

144

120

96

72

48

24 ............................................................

0 I I I I I I I I I I I I { I

Cm VlnlVlnlI Vla Cio Bas Pclo Fit Obo Clrt Basn Hrn Trpt Trbn Tba Prcn

Instrumental Section

Maximum Score-24

II Without RPGs [7_ With RPGs _ % Improvement

Conductor expressed verbal 100% ImprvmntRPGs Located Along Stage Perimeter4/25/91 Average = 83%

Figure 24. Case Study 10 comparison of existing stage without RPGs and with RPGs. The %Improvement, which is the ratio of the total score with RPGs divided by the total score without RPGsis also plotted. It can be seen that the average improvement was 83% with improvements as high as144%.

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Figure 25. Isometric illustration of VAMPS.

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Figure 26. Exploded axonometric illustration of VAMPS.

Figure 27. Cavani string quartet performing in front of VAMPS at the Cleveland Institute of Music.

Figure 28. Performance at Kohl Mansion, Burlingame, CA using VAMPS.

Figure 29. Artistic rendering of a full stage VAMPS with diffusive/reflective ceiling canopies.

Figure 30. Diffusive/reflective wall element which optimizes the diffuse backscattering of sound backat the source with forward sound projection.