Synthesis Theory I: Midterm
You may use any inanimate resource for this midterm. Your illustrious
instructor is the only human you may communicate with about this exam
until it is done. The exam is due at 2 p.m. sharp in room 316C
before class this Thursday. The exam may not be turned in late.
- Ear Physiology: Describe in your own words the anatomy of
the ear and how it works to enable us to hear sounds. What are the
three basic parts to the ear and what is the function of each part?
What is the pinna? What function does it serve in directional hearing?
How do we analyze the frequencies of sounds?
- Perception of Pitch: What determines the pitch of a soundwave
with many harmonic components?
- Loudness v Amplitude: Which is louder: (A) a 20 Hz sound
at 20 dBSPL or a 200 Hz sound at 19 dBSPL? (B) a
1,000 Hz sound at 50 dB or a 100 Hz sound at 60 dB? (C) a 10,000 Hz sound
at 80 dB or a 75 dB sound at 500 Hz? Explain the reasoning/methodology
for your answers.
- Range of Hearing: What is the highest frequency that you
can hear? Hint: use the osc program to write a soundfile with a
sinewave that increases in pitch from 1,000 to 22,000 Hz over 21 seconds.
Then listen to the soundfile and note at what time the sound becomes
inaudible. Use only high quality speakers/headphones such as the Meyer
Speakers in room 314C. There are no wrong answers, but I will be testing
you myself if I do not believe your answer. List your age and listening
environment as well as the highest frequency which you can hear.
- Linear Interpolation. You have a soundfile which you want
to transpose one octave lower using linear interplolation. Two adjacent
samples in the original soundfile have the amplitudes 0.232 and 0.562.
There is one additional sample which needs to be placed between these
two amplitudes in the final lower-pitches sound. What is the amplitude
of that sample?
- Just Noticeable Difference: If you have a soundfile which
contains whitenoise with a maximum amplitude of 0.5, what is the smallest
increase in maximum amplitude necessary to hear the noise increase in loudness?
What is the change in decibels for this increase in amplitude? Hint:
use the noise generating program from programming lab 1 to determine
your answer. Make a note of the listening conditions.
- Comb Filtering: If a comb filter has a delay of 100 samples
and the sampling rate is 44100, how many times per seconds will the sound
cycle through the comb filter delay? If the delay is set to 101 samples,
what is the frequency of delay, then? The frequency of the delay cycle
matches the pitch heard coming from the comb filter. Speculate on how
a pitch could be generated which is between that of the 100 sample delay
and the 101 sample delay.
- Wavelengths and Hertz: Dolphins are able to produce and
perceive sounds in the range from 20 Hz-150 kHz, while people
can only hear in the range from 20 Hz-20 kHz. (A) How many
more octaves can dolphins hear above humans (approximately)? Dolphins
use echo-location to catch prey. (B) How small of a fish can dolphins
track underwater? The speed of sound in water is 1,440 meters/second.
Assume that the fish must be at least 5 wavelengths of a 130,000 Hz sound
to be detected. (C) if a person could echo-locate fish underwater using
a 15,000 Hz sound, what is the size of the smallest fish to be detected?
How does this relate to the size of the person's mouth? Why can dolphins
hear to such high frequencies? If you are intersted in hearing the
sounds of dolphins, check out Folkways FW06132: Sounds and the Ultra-Sounds of the