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Acoustical Physics II
Acoustical Physics Midterm
109
Physics
Undergraduate 1
10/09/2011

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Term
Which part of the ear feels pressure fluctuations?
Definition
outer ear
Term
What is the Middle Ear's job?
Definition
Transforms pressure fluctuations of the outer ear in to vibrations of the small bones (the ossicles) in the middle ear
Term
The vibrations from the middle ear are sent to?
Definition
the cochlea located in the inner ear
Term
What happens in the inner ear?
Definition
vibrations are further transformed by stereocilia (hair cells) into neural impulses distributed by frequency
Term
Pinna
Definition
matches ear canal to outside world. OUTER EAR
Term
Meatus
Definition
(the passageway) conducts sound into head. OUTER EAR
Term
Tympanium
Definition
(the drum) transforms pressure fluctuations into displacement
Term
The Ossicles
Definition
The little bones in the middle ear
Term
Malleus
Definition
(the hammer) moved by Tympanium. Bone of middle ear.
Term
Incus
Definition
(the anvil) supported by ligaments that protect against loud percussion. Bone of middle ear.
Term
Stapes
Definition
(the stirrup) force multiplied by 1.3 because of lever action. Bone of middle ear.
Term
Cochlea
Definition
(the Snail) converts displacement into neural impulses. Inner ear.
Term
Auditory Nerve
Definition
neural impulses to brain. Inner ear.
Term
Semicircular canals
Definition
detect motion and orientation
Term
The location where in the Cochlea the stereocilia are stimulated is the?
Definition
Frequency
Term
The number of HC that are stimulated by the sound determines the ?
Definition
Intensity, or perceived loudness
Term
Which part of the ear protects you from loud noises?
Definition
Middle ear
Term
Hair cells are?
Definition
vibration sense organisms
Term
Formula for Sound Intensity Level
Definition
SIL = 10 Log ( I / Ithreshold )
Term
Loudness
Definition
Magnitude of the sensation produced by a sound; the “amount” of sound.
Term
The Human ear is what kind of sensor?
Definition
A non-linear sensor
Term
Intensity is perceived as?
Definition
Loudness
Term
Frequency is perceived as?
Definition
Pitch
Term
Vibration Recipe is perceived as?
Definition
Timbre
Term
The Fletcher-Munson Diagram is
Definition
a plot of the SIL (in dB) versus frequency for the SIL required to produce an equal sensation as that produced at 1000 Hz.
Term
In a Fletcher-Munson, the contours are of? The unit is?
Definition
of equal loudness level
phon
Term
One of the settings of a Sound Level Meter
(filter switch “A”) modifies the calibration of the
instrument to account for the frequency
dependence of human hearing.
Definition
Sound Level is then reported as dBA
Term
Loudness is measured in?
Definition
Sone
Term
Loudness scaling?
Definition
In cube roots, so an 8 person choir is twice (2x) as loud as a soloist. Because ∛8 = 2.
Term
Loudness Level
Definition
is equal to the SIL at 1000 Hz that produces the same magnitude of sensation.
Term
Loudness level measured in?
Definition
Phon
Term
Loudness increases approximately with the
Definition
cube root of intensity
Term
The loudness depends on:
Definition
frequency
Term
What is the threshold of intensity?
Definition
1 x10-12
Term
The Intensity of a sound wave is:
Definition
the energy radiated per unit time per unit area. [W/m2]
Term
The objective relative intensity level of sound is quantified as the
Definition
Sound Intensity Level (SIL) and the Sound Pressure Level (SPL)
Term
Sound Intensity Level (SIL) and the Sound Pressure Level (SPL) are measured in?
Definition
deciBels (dB)
Term
Sound Intensity Level equation and Ithreshold level
Definition
SIL = 10 Log( I / Ithreshold ),
with Ithreshold = 1 pW/m2
Term
Sound Pressure level equation and pthreshold
Definition
SPL = 20 Log (p/pthreshold )
With pthreshold = 20 μPa
Term
Humans are most sensitive in the frequency range:
Definition
2 kHz to 5 kHz
Term
The lowest detectable intensity (the threshold of hearing Ithreshold ) is about:
Definition
1 pW/m 2 or 1x10 -12 W/m 2
Term
The intensity at which one experiences pain (the threshold of pain) is about
Definition
1 W/m2
Term
The Sound Intensity Level is 10 times the logarithm of the ratio of the intensity of a sound and the threshold of hearing.
Definition
Term
0 dB corresponds to an intensity of?
Definition
1 pW/m2
Term
The threshold of pain is?
Definition
120 dB
Term
20An equal ratio of frequencies sounds like an:
Definition
Interval or equal distance
Term
20An octave is the pitch interval corresponding to a frequency ratio of:
Definition
2:1
Term
A semitone is:
Definition
1/12 of an octave
Term
20A cent (¢) is:
Definition
1/100 of a semi tone
Term
How many cents are in an octave?
Definition
1200
Term
The sensation of pitch is a property of human auditory perception that infers pitch from the:
Definition
repeat period
Term
Harmonics (including the fundamental) may be missing but we:
Definition
hear the difference frequency as well as the harmonics
Term
The Just Noticeable Difference (JND)
or difference limen is the
Definition
difference in pitch
(or loudness) that will elicit 75% correct
responses in a Two-Alternative Forced-Choice
test (2AFC) test.
Term
For sustained high pitched tones (>3 kHz):
the pitch perception:
Definition
rises slightly (goes sharp ♯) with loudness
Term
For sustained low frequencies (<500 Hz):
the pitch perception:
Definition
drops ( goes flat ♭) with loudness.
Term
For pulsed tones:
the pitch perception:
Definition
drops slightly ( goes flat ♭) with increasing loudness for all frequencies
Term
Tones are indistinguishable if they are closer than a:
Definition
critical band width
Term
Pitch interval is proportional to the logarithm of:
Definition
the ratio of the frequencies
Term
The intensity of sound decreases with the:
Definition
square of the inverse of the distance from the source in an open area
I / I0 = (r0 /r) 2
Term
The Sound Intensity Level (SIL) diminishes with distance thus:
Definition
SIL= SIL0 – 20 Log (r / r0 )
Term
SIL1 =
Definition
SIL2 – 20 Log (r1 / r2)
Term
Wave motion is characterized by: (6 characteristics)
Definition
Reflection
Refraction
Diffraction
Doppler Shift
Beats
Interference
Term
specular reflection
Definition
like mirror reflection
Term
Huygens Principle:
Definition
every point on the wave is the source of a new (spherical) “wavelet.”
Term
Doppler Shift equation
Definition
f observed ≈ f source ‧ [1 + vobserver /v ][1+ vsource
Term
Reflection
Definition
is the return of a wave from a change in a medium.
Term
Refraction
Definition
is bending of the wave due to velocity variation along the wavefront.
Term
Diffraction
Definition
is the bending of the wave around obstacles because of Huygen’s Principle
Term
Doppler Shift
Definition
is the change in frequency due to the relative motion.
Term
Beats are
Definition
intensity modulations in time due to coherent addition of waves of near equal frequency.
Term
Interference is
Definition
spatial modulation of intensity due to the coherent addition of nearly equal frequency waves at different points in space
Term
20If two tones have frequencies separated by
less than a critical band width they add
coherently and the amplitudes of waves are
added. Then the intensity will be
Definition
proportional
to the square of the the combined amplitudes.

Icoherent = (a1 + a2 ) 2 = a1 2 + a2 2 + 2 a1a2
Term
Incoherent addition of waves is equal to
the sum of their independent intensities
if they are
Definition
not within the critical bandwidth

Iincoherent = a12 + a2 2
Term
Standards for "Good" Acoustics (7)
Definition
Clarity
Uniformity
Envelopment
Smoothness
Reverberation
Performer Satisfaction
Freedom from noise
Term
Haas or Precedence Effect
Definition
The earliest sound that arrives determines the sense of the origin of a sound, even if the later (<100 ms) reflections are louder.
Term
The sound reflects many times, each time:
Definition
losing energy to the reflecting surface.
Term
The quantity α is the
Definition
absorptivity of the surface
Term
The intensity of the sound that is lost in a reflection is
Definition
ΔIlost = α Iin.
Term
The intensity of the reflected wave is
Definition
Ireflected= (1-α) Iin
Term
The reverberation time is the time
Definition
for the intensity to decay by a factor of 10 –6 (- 60dB) of its initial value
Term
Sabine equation
Definition
I = Io ‧ 10 – 6 (t/TR)
Term
Sabine equation (in terms of reverberation time)
Definition
TR = 0.16 V/Se
Term
Direct sound should come:
Definition
first
Term
V is:
Definition
is the volume of the room.
Term
Se is the
Definition
“effective surface area” of the walls S1 , floor S2 and ceiling S3 (in sabin) etc
Term
Se = α1 S1 + α2 S2 + α3 S3 + α4 S4 +…
Definition
Term
“Western Music” is based (approximately) on the
Definition
ratio of whole numbers
Term
With Just Temperament it is
Definition
impossible to tune all notes or tones of the chromatic scale so that they are all in tune, that is, the correct ratio for all keys.
Term
20Equal Temperament intonation is a compromise in which the semitones
Definition
are precisely 100 ¢ or a ratio of 1.05946… of its neighbor.
Term
Just Temperament uses
Definition
integer ratios of adjacent notes in the chromatic scale
Term
Equal Temperament uses
Definition
a constant ratio of adjacent notes in the chromatic scale
Term
fundamental frequency equation
Definition
f = 1/(2L) √(T/ μ)
Term
Standing waves on the string are responsible for
Definition
the harmonic series of stringed instruments
Term
A musical instrument comprises four important components
Definition
a mechanical energy source
a frequency generator
a frequency filter
an antenna
Term
Frequency of nth harmonic:
Definition
fn = [n/(2L)] ‧ √(T/ μ)]
Term
The modes that will be present are those that are
Definition
excited.
Term
Energy source can excite
Definition
selected modes
Term
The coupling of the string to the sound board will
Definition
accentuate or attenuate various frequencies
Term
The timbre of a musical instrument (also known as musical recipe) is determined by the
Definition
excitation, frequency generation, filtering and broadcast of the harmonics
Term
The node-antinode distance is
Definition
¼ λ
Term
Marsenne Equation (frequency of nth harmonic). Used for string instruments
Definition
fn = [n/(2L)] ‧ √(T/ μ)]
Term
The timbre of bowed strings is affected
Definition
(1) by the properties of strings,
(2) by the effects in bowing and
(3) by the frequency resonances of the instrument.
Term
The Stick-Slip Mechanism causes the string to
Definition
vibrate when rubbed by the bow
Term
The coupling of the string to the sound board will
Definition
accentuate or attenuate various frequencies
Term
The Difference limen for pitch is about
Definition
1/30 the critical band width
Term
Pitch Interval corresponding to f2 and f1 :
Definition
₧ = 3986 ¢ ‧ Log (f2 /f1 )
Term
Inverse Square Law:
Definition
I / I0 = (r0 /r) 2
Term
The Sabine Equation
Definition
TR = 0.16 V/Se

Se = α1 S1 + α2 S2 + α3 S3 + α4 S4 +…
Term
Velocity of a wave on a string
Definition
vstring = √T/ μ
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