Sound speed and frequency
The speed of sound in air is given by v=331.4+0.6T. At 20°C, what is the speed of sound?
v=331.4+0.6T=331.4+0.6(20)=331.4+12=
343.4 m/s
A 2 m string fixed at both ends supports a standing wave with two loops. What is the wavelength?
λn=2L/n.
“Two loops” → n=2
λ=2x2/2
wavelength=2
Two tones of 256 Hz and 260 Hz are played together. What beat frequency do you hear?
fbeat=∣256−260∣
4 Hz
A resonant circuit peaks at 1000 Hz with a bandwidth of 250 Hz. Find its Q factor.
4
The vocal tract is modeled as what kind of tube?
Open-Closed
A sound wave has a wavelength of 1.7 m and frequency of 200 Hz. What is its speed?
v=fλ=200×1.7=
340 m/s
The fundamental frequency of a 1.5 m string is 100 Hz. What is its third harmonic?
f1=100
f1x3=300
300 HzA tuning fork of 440 Hz produces 3 beats/sec with a guitar string. What are the two possible guitar frequencies
Take frequency and +- 3
437 and 443 Hz
A system resonates between 500–700 Hz. What type of filter is it?
Band Pass
If a person’s vocal tract is 18 cm long, find their fundamental frequency (v = 340 m/s)
convert to meters
f=v/4L
340/4(.18m)
340/0.72
~472 Hz
If a sound wave travels at 340 m/s and you measure its wavelength as 0.68 m, what is the frequency?
f=λv=0.68340=
500 Hz
A 0.5 m string has a 4th harmonic frequency of 440 Hz. Find the fundamental frequency
440/4=110
110 Hz
If you tighten the guitar string slightly and the beat frequency increases, is the string’s frequency moving toward or away from 440 Hz
Tension increases->frequency increases
if originally 3, may increase to 5, meaning the frequency moves away from 440.
Away
If a filter passes all frequencies above 300 Hz, what kind of filter is it?
High Pass
Increasing the tension in the vocal folds affects pitch in what way?
Increases pitch
A sound wave has a wavelength of 0.85 m in air.
What is the frequency of the wave if the speed of sound is 340 m/s
f = v / λ = 340 / 0.85 = 400 Hz
A guitar string of length 1 m has a fundamental frequency of 150 Hz.
What is the wavelength of the second harmonic
2L/n 2
2(1)/2 = 1 m
A 600 Hz tone interferes with another of unknown frequency to produce 5 beats per second. Find the two possible frequencies.
600 +- 5
595 or 605 Hz
The lower and upper cutoff frequencies of a resonator are 900 Hz and 1100 Hz. Find bandwidth and Fpeak
Fpeak=1000 Hz
What are the frequencies that the vocal tract resonant at called?
Formants
The speed of sound in air is 340 m/s. If a tuning fork produces a frequency of 170 Hz, what is the wavelength of the sound?
λ = v / f = 340 / 170 = 2 m
2 m
In an open-closed tube 0.4 m long, find the fundamental frequency if the speed of sound is 340 m/s.
Step 1: find wavelength -> 1.6
f1=340/1.6 =212.5Hz
Two tuning forks produce a beat frequency of 5 Hz.
If one fork vibrates at 340 Hz, what are the two possible frequencies of the other fork.
340 +- 5
335 or 345
A string vibrates strongly when plucked near a certain frequency. Why?
It’s at or near its natural frequency
A high-pitched voice has harmonics spaced farther apart or closer together?
Farther Spaced