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comd 401 acoustics of speach and hearning april 05


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in physical terms what is work
force times displacement
what is the principle of conservation of energy
energy can neither be created or destroyed but it can be converted into different types of energy
when a wave propagates through a medium what physical property is actually propagating
what is expressed in units of joules
what is power
it is the rate at which work gets done in terms of time
what are the units of measure for power
joules per second
what is a word for power per unit area
in acoustics what is intensity
power per unit area
watts per unit area
what was the fist expression of sound expressed in a ratio
The Bell unit
what was one problem with the bell unit ad what was the solution
the bell unit was still to large
the solution is to creat deci-bells
what is potential energy?
energy that is stored and can be converted to kinetic energy or work
what is kenetic energy?
the energy of potion
what is the work energy theorem?
Any change in the kenetic energy of a body is the result of having work done on it
what are the two types of energy?
potential energy and kenetic energy
what is energy in non-formula terms?
energy is the ability or capacity to perform work
what two physical factors affect the perception of the loudness of a sound?
the power of the sound source and the surface area which this power is spread over.
what is a word for "power per unit area"
What are the units of measure for intensity?
In Acoustic intensity is measured in watts
what do we perseive as loudness?
If our ears do not detect absolute pressure then what do they detect
they detect the fluctuations in pressure
why do we express intensitys on scientific notations?
becuse the human ear can hear such a wide range of sounds that it is much easier this way
What is the difference between an interval system versus a ratio system?
A interval system is from 1-10^15 and it is evenly distributed. A ratio is comparesomething to a geven reference and is compared to that reference value
What is the dynamic range of the auditory system and what determines its boundaries?
It is the distance between the threshold of audibility and the threshold of pain.
"In arbitrary. Absolute units of quantification, what is the dynamic range of the auditory system?
1 unit to 10^`15
What is one practical problem caused by the answer the dydnamix range of audioty hearing described in a quantitative number?
A practical problem is that the numbers are too large and hard to work with.
Decribe why people can both very short duration changes and can also detect very long one's
the mutiply indicator theory states that a person has short nueron reseptures and also has very ling one's
Sketch the human audibility curve

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Sketch the function that relates detection threshold to the duration of a sound

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Sketch the function that relates detection threshold to the bandwidth of a sound

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What is the concept of the inverse square law?
as you move farther away the sound source the pressure decreases by -6 db
what are three things that can happen to a wave when it encounters an interface?
Reflected / transmission/ absorbed/ diffraction
what is a sound shadow
this is the "shadow" that the barrier creates when it blocks the wave.
Under what conditions does a sound shadow occur?
THE WAVE is smaller then then the barrier and it gets blocked the rest of the wave can go around it, this normally occurs from a high frequency wave not a low frequence
What are the different sound fields?
Diffuse sound field - sound particles are equally distributed though out the field/ Focal (beamy) is when the sound particles are not equally distributed but randomly and could be clumped together in certain places
what is an anechoic room
are rooms that are engineered to have no echo
Define psychoacoustics?
The study of the brain's perception of, and reaction to, all aspects of sound. (i.e., intensity, time of arrival differences, reverberation', et al.)
describe the general concept of a "threshold"
a threshold is the maximum or minimum of tolerable sound or minimums sound someone can hear.
Describe the concept of sensitivity as it pertains to audibility
this is the minimum input that a sound source (ear) needs to be able to make a sound audible to the listener
What is the relationship between sensitivity and threshold?
Because the ear is so sensitive it can go through the dynamic range and still be able to distinguess the difference between sound s that are very close together. The ear is cery sensitive even though it has such a large dynamic range
what is a person's threshold of audibility?
the dynamic range of audibility
What are acoustic variables are manipulated in a task estimating auditory sensitivity?
The sound that is put into the person’s ear, and the background noise, and the level of sound pressure.
Be familiar with the basic human audibility curve
The human audibility curve shows the dynamic rage as it purtains to the graph. It also shows how people her at different levels this graph is very important when converting db (hl) to db (spl)
Explain how sound shadow of the head influences intramural intensity differences?
Your ability to localize the source of sound in high frequency is predicated on this intramural intensity difference, which is based on head shadow. If you can’t predict where the sound is coming from, then your brain won’t be able to know where you are talking. The brain also ignores later sounds
what is a phons
The phon is a unit that is related to dB by the psychophysically measured frequency response of the ear.
What is scon
The sone is derived from psychophysical measurements which involved volunteers adjusting sounds until they judge them to be twice as loud.
what is the relationship between phons and scon
perceived loudness to phons. A sone is defined to be equal to 40 phons.

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