Sound Audiology
description
Transcript of Sound Audiology
SoundAudiology
Perry C. Hanavan, Au.D.
Audiologist
Sound
Vibration
Perception
Propagation of Sound
Condensations____________
Example of molecular motionComponents of sinusoidTransverse wave simulationApplet: Square, triangle, simulation
Components of Sound
Physical Psychological
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Intensity Loudness
Frequency ________
Duration Length
Intensity
Decibel– Unit of measure of intensity– dB = 10logR (R=ratio)– dB = 20logR
Problem
Human hearing intensity dynamic range is quite broad
1 Softest sound
1,000,000,000,000 Loudest sound
Intensity Dynamic Range110100100010000100000100000010000000100000000100000000010000000000100000000000100000000000010000000000000100000000000000
Honey I Shrunk the Kids
1,3,5 or 1, 4, 8, 12 etc. reduces dynamic range somewhat
1, 10, 100, 1000 shrinks a bit more
– Yet, dynamic range is quite large
Solution
Ratio
Compare intensity value (number) to reference
8:4 (really 2:1)
Aha! Ratio Compare 2 Numbers1/1 =110/1 =10100/1 =1001000/1 =100010000/1 100000/1 1000000/110000000/1 100000000/1 1000000000/1 10000000000/1100000000000/11000000000000/110000000000000/1100000000000000/1
Logarithms!!
Now that a ratio has been converted
Next step: Convert ratios to logs (base 10)
Lets Work with Logs!!!
1 = 010 = 1100 = 2100000000000000 = ?14.1 = -1.01 = -2.00000000001 = ?-11
So is that a decibel?
So far we have
1. Converted a ratio to a number (10:1=10)
2. Converted the ratio to a log (10=1)
We have created a ____ (A.G. Bell)
There are 10 decibels in a bel2 bels = 20 decibels
8 bels = 80 decibels
WOW!!!
Decibel = 10 log _____
A decibel consists of:
1. Ratio
2. Log
3. X10
That was easy, let’s practice:
Integer: 10 X 10 = 100Log: 1 + 1 = 2
Integer: 1000 X 1000 = ?Log: 3 + 3 = 6
Now take the log times 10 to convert to decibels
Not bad, let’s try this:
Integer: 100 / 10 = 10Log: 2 - 1 = 1
Integer: 1000000 / 100 = ?Log: 6 – 2 = 4
Now take the log times 10 to convert to decibels
Ok, I can do that, but…
Some numbers are quite easy to work with in logs
However, some numbers you need to use a calculator or look in a CRC book of tables
Or you can memorize several numbers and calculate lots of logs
Hint: log = bel
Oh, one more thing:
Measures of ________ are often made in Sound Pressure Level (SPL) rather than Intensity Level (IL)IL: amount of energy flowing thru a 1cm2 surface areaSPL: amount of pressure exerted on a 1cm2 surface areaIL = SPL2
dBIL=10logR equals dBSPL=20logR
dB Intensity Level
Measure of energy
Reference 1.0 X 10 -16 watts/cm2
or
.0000000000000001 watts/cm2
dB Sound Pressure Level
Measure of force or pressure
Reference 20 microPA
Ratios in IL and SPL
Sound Pressure Level
20/20 = 1:1
40/20 = 2:1
60/20 = 3:1
200/20 = 10:1
Intensity Level
1.0x10-16/1.0x10-16
2.0x10-16/1.0x10-16
3.0x10-16/1.0x10-16
4.0x10-16/1.0x10-16
1.0x10-15/1.0x10-16
dBIL=10logR or dBSPL=20logR
Ratio No. Log dBIL dBSPL 1:1 1 0 0 02:1 2 .3010 3.0 6.03:1 3 .4771 4.8 9.64:1 4 .6020 6.0 12.05:1 5 .6990 7.0 14.06:1 6 .7781 7.8 15.67:1 7 .8451 8.5 17.08:1 8 .9030 9.0 18.09:1 9 .9542 9.5 19.010:1 10 1.000 10.0 20.0
Can you do this?
Double SPL?
Double IL?
Triple SPL
Triple IL?
Quadruple SPL?
Quadruple IL?
What about this?
Halve IL?
Halve SPL?
Practical Applications of dB
If a child’s ear canal is ___ times as small as an adult, what happens to the SPL in the child’s ear canal?
If a student is 3 times closer to the teacher’s voice than another, how much more SPL reaches the child sitting near the teacher?
Hearing Level
Converting SPL to HL (HTL)