Sound Wave Properties. What we have learned:. Sound is a longitudinal wave. (A mechanical wave caused by a vibration) Sound (mechanical wave) requires a medium . Wavelength and frequency are inversely related. Molecules interact , producing sound
v= velocity of sound in air
T=temperature of air in °C
v=331 + (0.6)T
1. Tommy and the Test Tubes have a concert this weekend. The lead instrumentalist uses a test tube (closed end air column) with a 17.2 cm air column. The speed of sound in the test tube is 340 m/s. Find the frequency of the first harmonic played by this instrument.
L = λ/4
4 x L = λ
4 x .172 = .688 m
v = f λ
340 = f (.688)
f = 494 Hz
2. Matt is playing a toy flute, causing resonating waves in a open-end air column. The speed of sound through the air column is 336 m/s. The length of the air column is 30.0 cm. Calculate the frequency of the first, second, and third harmonics.
2 x L = λ
2 x .30 = .60 m
v = f λ
336 = f (.60)
f = 560 Hz. (first harmonic)
2nd harmonic = 560 + 560 = 1120 Hz.
3rd harmonic = 1120 + 560 = 1680 Hz
A mosquito’s buzz is often rated with a decibel rating of 40 dB. Normal conversation is often rated at 60 dB. How many times more intense is normal conversation compared to a mosquito’s buzz?
On a good night, the front row of the concert may result in a 120 dB sound level. An IPod produces 100 dB. How many IPods would be needed to produce the same intensity level as the front row of the concert?
A trumpet player plays a C note of 524 Hz while traveling in a convertible at 24.6 m/s. If the car is coming toward you, what frequency should you hear? Assume the temperature is 20°C.
p.405 # 1-5 (use table 15-1 for the speed of sound in various media)
p. 409 #6-8 Read Carefully!