PHY Exam 2
Terms in this set (56)
What membrane terminates the outer ear?
the eardrum (tympanum)
What are the bones in the middle ear called?
What tube connects the middle ear to the oral cavity?
What is the main function of the semicircular canal in the inner ear?
Horizontal-vertical detectors for balance
What is the spiral organ in the inner ear called?
What happens to the cilia when the basilar membrane responds to the sound?
the stereocilia (hair cells) bend
What part of the basilar membrane responds the most to low-frequency sound?
In addition to transmission through the outer ear, how else can sound reach the inner ear?
Vibrations to the skull
At low frequency, the critical bandwidth remains nearly constant. (T/F)
How are the sounds of lower frequency localized?
Detecting phase differences and arrival times at the two ears
How are sounds of higher frequency localized?
The orientation of the pinna
What is the precedence effect?
How we localize sounds in everyday settings
According to Fechner's law, how do sensations increase as stimuli are increased by multiplication?
Addition; one step on a scale
Pitch depends mainly on what physical parameter?
What other physical parameters does pitch also depend on?
What is the envelope of a sound?
The attack, sustain and decay of sound
What is a logarithm?
The function of a number which outputs an exponent of a base equating that number.
In what units is sound intensity measured?
What reference level is used to measure sound intensity level?
What is meant by a free field?
An environment in which there are no reflections
How large is the "just noticeable difference" in sound level?
How much does the sound level decrease in a free field when the distance from the source is doubled?
In air, how does p change as the temperature increase?
It decreases (see table: https://en.wikipedia.org/wiki/Density_of_air)
In air, how does c change as the temperature increases?
It increases, but not by as great a factor as p decreases (see table: https://en.wikipedia.org/wiki/Density_of_air)
In air, how does pc change as the temperature increases?
It decreases (see table: https://en.wikipedia.org/wiki/Density_of_air)
What is the approximate sound level in normal conversation?
If each of two sound sources alone produces a sound level of 55 dB at a certain point, what will the level most likely be at that point if both sources are active?
Doubling the power results in a +3 dB change, so 58 dB
In what units is loudness level expressed?
In what units is loudness expressed?
What generally happens to loudness as the bandwidth of a certain source is increased while the sound level stays constant?
The loudness increases once the critical bandwidth is exceeded.
By approximately how many dBs must the A-weighted sound level increase in order to double the loudness of a complex tone.
What is the average dynamic range of a single note played on a musical instrument?
10 dB for a bassoon
What is backward masking?
The masking of a tone by a sound that begins a few milliseconds later
Is it easier for a tone of lower frequency to mask a tone of a higher frequency, or vice versa?
A pure tone masks tones of higher frequency more effectively than vice versa
Six categories of sound generators:
1. Vibrating solid bodies
2. Vibrating air columns
3. Flow noise
4. Rapid changes in pressure/temperature
5. Interaction of moving solid w/ fluid, or moving a fluid with a solid
6. Shock waves
What percentage do modern airplanes convert mechanical power output as acoustic power?
What percentage do automobiles convert mechanical power output as acoustic power?
What percentage do trucks convert mechanical power output as acoustic power?
What does Lx represent?
The sound level exceed x percent of the time, with different values being x
What does Leq represent?
The dB of a steady noise that gives the same total energy over the same time period
Atmospheric turbulence affects sound outdoors because...?
Sound waves need a medium to propagate. If the atmosphere is turbulent, it would lead to scattering of sound waves due to velocity fluctuations of the medium
Temperature gradients affect sound outdoors because...?
The speed of sound waves depends on the temperature of the gas it is traveling in. Faster in warm air near the surface of the earth, and as the temperature decreases w/ altitude, upward refraction occurs.
Wind gradients affect sound outdoors because...?
Sound propagation along the wind would bend downwards while sound propagation against the wind would bend upwards.
Atmospheric absorption affects sound outdoors because...?
Due to the molecules present in the atmosphere absorbing sound energy in order to convert it into heat, the sound level is attenuated with distance for the wave traveling. Atmospheric absorption occurs mainly at high frequencies.
Reflection from the earth's surface affects sound outdoors because...?
When the source and receiver are at ground level, the sound wave reflected from the ground interferes with the direct wave, which affects the sound propagation.
Type of ground cover affects sound outdoors because...?
If the ground surface is smooth, sound attenuation will be less. If the surface has vegetation, the attenuation of sound would depend on absorptive and reflective properties of the vegetation.
What are monopole sound sources?
A source that radiates equally in all directions, in this case the entire vibrating surface radiates in phase. (ex. siren, free chemical explosion)
What are dipole sound sources?
Two monopole sources separated by a distance and vibrating in phase opposite to each other. (ex. moving fan blade, noise of air blowing through a grill, etc.)
What is a quadrupole sound source?
Consists of four parts, which vibrates alternatively in phase. (ex. gas jet in a jet airplane engine)
What does an accelerometer measure?
The vibration of an object
How does an accelerometer work?
It consists of a mass suspended by a spring, a damper and a displacement transducer. When fixed to the vibrating body, accelerometers generate electrical signals proportional to the acceleration of the mass and helps to determine what surfaces are vibrating strongly at the frequency of the most prominent noise component in the spectrum.
What is the main source of sound in trucks at high speeds?
The tires. Tire noise at 55 mi/hr ranges from 75-95 dBA
What is the main source of sound in trucks at low speeds?
The exhaust and fan noise, which are must less compared to that generated by tires at high speeds.
What is the max pass-by noise from passenger cars in most states?
80 dBA, which is measured 1.5m from the road center and 1.2m above the ground while the vehicle is not going at max acceleration and no more than 45 m past the microphone.
What is the max noise level measured 100ft from the tracks for locomotives manufactured after 1980 per the EPA?
List was to reduce railroad noise:
1) usage of mufflers equipped in diesel locomotives (-6 dB)
2) usage of welded rails (-3 dB)
3) careful maintenance of rolling stock
4) usage of barrier walls around retarders in rail yards (-20 dB)
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