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Microphone Specifcations

Microphones measure broadband sound pressure levels from a variety of sources.

When the microphone signal is post processed, the frequencies can be correlated with

the sound source, and if necessary, related back to the wavelength of the sound.

Acoustical measurement of this sound, through the use of high-precision condenser

microphones, provides a better understanding of the nature of the sound. There are a

number of microphones that will work and measure pressure variances. ommon

diameters for condenser microphones are .!"#$, "#%$, #%%$ and !.%$. The trick is to

determine which microphone will offer the best solution for a required application. When

choosing the optimum microphone, the parameters to look at include the type of

response field, dynamic response, frequency response, polari&ation type, sensitivity

required, and temperature range. There are also a variety of specialty type microphones

for specific applications. 'n order to select and specify a microphone, the first criteria

that needs to be looked at is the application and what the sound and environment

represent.

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(ig. (ree field mic

The free-field microphone is most accurate when measuring sound pressure levels that

radiate from a single direction and source, which is pointed directly )%o incidence angle*

at the microphone diaphragm, and operated in an area that minimi&es sound reflections.

A free-field microphone is designed to measure the sound pressure at the diaphragm,

as it would appear if the microphone were not present

Data Acquisition System (DAQ)+ata acquisition )+A * is the process of measuring an electrical or physical

phenomenon such as voltage, current, temperature, pressure, or sound with a

computer. A +A system consists of sensors, +A measurement hardware, and a

computer with programmable software. The components of data acquisition systemsinclude

ensors, to convert physical parameters to electrical signals.

ignal conditioning circuitry, to convert sensor signals into a form that can be

converted to digital values.

Analog-to-digital converters, to convert conditioned sensor signals to digitalvalues.

+ata acquisition applications are usually controlled by software programs

developed using various general purpose programming languages such

as Assembly , /A ' , , 00 , 1 , (ortran , 2ava , 3ab4'5W , 3isp , 6ascal , etc.

https://en.wikipedia.org/wiki/C_Sharp_(programming_language)https://en.wikipedia.org/wiki/Java_(programming_language)https://en.wikipedia.org/wiki/LabVIEWhttps://en.wikipedia.org/wiki/Pascal_(programming_language)https://en.wikipedia.org/wiki/Java_(programming_language)https://en.wikipedia.org/wiki/LabVIEWhttps://en.wikipedia.org/wiki/Pascal_(programming_language)https://en.wikipedia.org/wiki/C_Sharp_(programming_language)

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Signal Conditioning

ignals from sensors or the outside world can be noisy or too dangerous to measure directly. ignal

conditioning circuitry manipulates a signal into a form that is suitable for input into an A+ . This circuitry

can include amplification, attenuation, filtering, and isolation. ome +A devices include built-in signal

conditioning designed for measuring specific types of sensors .

Analog-to-Digital Converter (ADC)

Analog signals from sensors must be converted into digital before they are manipulated by digital

equipment such as a computer. An A+ is a chip that provides a digital representation of an analog signal

at an instant in time. 'n practice, analog signals continuously vary over time and an A+ takes periodic

7samples$ of the signal at a predefined rate. These samples are transferred to a computer over a

computer bus where the original signal is reconstructed from the samples in software.

Computer Bus

+A devices connect to a computer through a slot or port. The computer bus serves as the

communication interface between the +A device and computer for passing instructions and measured

data. +A devices are offered on the most common computer buses including 8 /, 6 ', 6 ' 59press,

and 5thernet. More recently, +A devices have become available for :%".!! Wi-(i for wireless

communication. There are many types of buses, and each offers different advantages for different types

of applications.

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