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Microphones
Instrumentation and Electroacoustics
34
Audiology
Graduate
03/08/2017

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Cards

Term
___ is a transducer that transduces acoustical energy (sound
pressure) into electrical energy (voltage) for the purpose of transmitting or recording
Definition
microphone
Term
Microphone:
-Acts as a ___ sensor calibrated to the measurement of small variations in air pressure
-Most commonly, vibration of a thin membrane (diaphragm) is
used to produce a ___ proportional to the ___ of the vibration
Definition
pressure; voltage; magnitude
Term
Microphone: Transduction is accomplished by...
-___ generation (dynamic microphones)
–___ charge (condenser microphones)
–___ generation (piezoelectric microphones)
Definition
Electromagnetic; Capacitance; Piezoelectric
Term
Microphone:
-the amount of current depends on how the distance of the diaphragm changes in relation to the ___
Definition
backplate
Term
Condenser Microphone:
-Contains a diaphragm mounted above a back plate to form a ___
-Internal charge held ___; voltage varies as pressure actuates the ___. Requires an ___ voltage supply or a charged diaphragm
-Acoustical performance determined by ___ dimensions
-Small signal – requires a ___
Definition
capacitor; constant; diaphragm; external; physical; preamplifier[image]
Term
Storage of electrical charge
Definition
capacitor
Term
Most common type of condensor microphone used in audiology and hearing science applications (including modern hearing aids)
Definition
Electret microphone
Term
Electret Microphone:
-Diaphragm permanently ___ like a magnet (electrostatic magnet), avoiding the necessity of a biasing DC voltage
-It has a wide ___ range in terms of frequency and a flat frequency response, that is, ___ energy across the wide dynamic range
-This mic is ___ (having its own charge) and can last for more than ___ years
-not ___; has a charge
Definition
polarized; dynamic; equal; self-biased; 100; neutral
Term
An electronic device that amplifies a signal to prepare it to be amplified or processed by an amplifier; amplifies signal before any processing occurs
Definition
pre-amplifier
Term
Generally, the function of the pre- amp is to amplify a microphone’s tiny signal to “___-___” (voltage necessary to drive the amplifier)
Definition
line-level
Term
Condenser microphone advantages:
-Can be manufactured to very ___ size
– Excellent ___ response (better than dynamic mics)
– Excellent ___ quality
– Usually low internal ___
Definition
small; frequency; sound; noise
Term
Condesner microphone disadvantages:
-May require ___ power source
– More ___ in construction than dynamic mics
– Has maximum ___ it can handle
– Affected by ___ and ___
– Cheap or malfunctioning condensers will create internal ___
Definition
external; complex; SPL; temperature; humidity; noise
Term
Dynamic Microphone:
-___ wire coil attached to a robust diaphragm
-Unmovable magnet produces a ___ ___
-Moving diaphragm moves the coil within the magnetic field, inducing a measurable ___. The reverse of the way a ___ works.
-Commonly used for ____ and ___ performances on stage
Definition
Movable; magnetic field; current; speaker; musical; dramatic
Term
-Note that the dynamic microphone has the following components: diaphragm, magnet, coil, and wires that carry the electrical signal into an electrical system.
-The diaphragm is attached to the ___. The coil moves in synchrony to the ___ ___ when the diaphragm vibrates in response to an incoming acoustic signal.
Definition
coil; sound wave
Term
Dynamic microphones are known for ___ reduction and bass ___-___. These microphones are used for ___ ___ systems, recording, and have a ___ shape to concentrate energy. They are usually ___ in cost. Dynamic microphones can record both ___ and ___ signals.
Definition
noise; roll-off; public address; cone; low; digital; analog
Term
The dynamic microphone is often used in clinical audiology especially for the test-microphone monitor on the ___. ____, rather than conventional, magnets are sometimes used for the dynamic microphone as they are more powerful. Neodymium microphones are ___, with a uniform frequency response and higher ___ output.
Definition
audiometer; Neodymium; smaller; volume
Term
Dynamic Microphone advantages:
-Simple and ___ to construct
-Can handle ___ SPLs (hard to overdrive)
-Resistant to ___ change and ___
-Generally more ___ (less delicate) than other microphone types
-Poor low-frequency response reduces noise
-No internal noise
Definition
inexpensive; high; temperature; humidity; robust
Term
Dynamic microphone disadvantages:
-___ and ___ than condenser mics
-___ response –takes longer to stop and start moving, reducing sensitivity to ___ sounds
–Poorer ___ quality
–Poorer ___ response
Definition
Larger; heavier; Slower; transient; sound; frequency
Term
The quality and utility of a microphone is dictated by what 8 characteristics?
Definition
sound source, equipment, cost, physical setting, sensitivity, frequency response, directionality, and noise
Term
Amount of electrical output produced by a microphone for a given SPL input
Definition
sensitivity
Term
Sensitivity:
-The relationship between the size of the output ___ and the input ___ ___
-If two microphones are subjected to the same SPL and one puts out a ___ voltage signal, that one is considered to be the more sensitive microphone
Definition
voltage; sound pressure; higher
Term
Is higher sensitivity in a microphone always better?
Definition
No. It is if you are trying to amplify sound in a hearing aid for soft sounds. If there are loud sounds though it could damage the microphone.
Term
The pattern of the microphone’s intensity output for inputs at different frequencies (amplitude or voltage as a function of
frequency)
Definition
Frequency Response
Term
Frequency Response:
-Often expressed using a ___ (i.e., 20 – 20,000 Hz) and an expression of the ___ in the response (i.e., 100 dB SPL +/- 3 dB at 1000 Hz)
-___ frequency response is a desirable response
Definition
range; variation; flat
Term
Equal sensitivity at all angles
Definition
omnidirectional
Term
-No microphone is ___
-“excellent for ___ discussions, ___ groups, and so forth”
Definition
omnidirectional; group; vocal
Term
Bi-directional:
-Strong output level or sensitivity at __ and __ degrees
-Weak output level or sensitivity at __ and ___ degrees
Definition
0; 180; 90; 270
Term
Bidirectional microphones pick up sounds from ___ and ___ while rejecting sound from ___ ___
Definition
front and back; both sides.
Term
High sensitivity at 0 degrees but reduced as sound moves off of the axis
Definition
Unidirectional
Term
Unidirectional mikes, also called cardiod mics because they are similar in configuration to the ___ ___, pick up sound from one direction (the front), and separate speech and other desired signals from background noise.
Definition
human heart;
Term
The unidirectional microphone is good for ___-___ speech audiometry, lectures, and so forth. However, on occasion, the unidirectional microphone exhibits an undesirable proximity effect that boosts ___ frequencies, especially when the speaker’s mouth is near the microphone. This is why we often see TV interviewers moving the mic ___ and ___ to avoid a proximity effect
Definition
live-voice; low; back and forth
Term
-The frequency response of a microphone affects its overall ___ (shape of the polar plot)
-___ frequencies travel in a straight line longer before they spread out whereas ___ frequencies spread out from the get go
Definition
directionality; higher; lower
Term
Noise:
-Because of the small size of the moving parts, microphones produce a very ___ signal. A signal must be ___ (~ x1000) to be heard. Unwanted noise will also be ___
Definition
small; amplified; amplified
Term
Noise:
-Dynamic microphones produce no ___ but the circuitry in condensers can create noise if not designed ___
-Noise can also be created by physical ___ through the body of the microphone
-Microphones are sensitive to ___ and ___ noise
Definition
noise; properly; vibrations; wind; breath
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