Sound Lab

Objective: Observe and analyze the characteristics of different waves created by tuning forks and the human voice

Lab Equipment:

- Lab Pro with Microphone

- computer

- tuning fork

Data Collection:

For this lab we needed to collect five different wave patterns using the Lab Pro setup. The setup consisted of a microphone that detected pressure variations in the air connected to a computer. Three wave patterns were human voice recordings of two members of our group. The other two wave patterns were created by striking a tuning fork near the microphone and recording the pattern. Below are the collected wave patterns and corresponding analysis.

Graph #1

This is a graph of one group member saying "AAAAA" over a collecting period of 0.03 seconds.

Questions:

a) This wave does appear to be periodic since the collected wave has a fairly consistent repeating pattern between the highest peaks.

b) Approximately 3.5 waves are shown in this sample. We determined this number by measuring the length of the total display and the distance between peaks on the computer screen and dividing the first by the second.

c) The length of this data collection period could be compared to the duration of a single frame on a traditional television which lasts about 0.02 seconds.

d) Period = T = (collection time)/(# of wave repetitions) = 0.03/3.5

               = 0.0085 seconds (error = 0.0005 s)

e) Frequency = 1/T = 1/0.0085 = 118 hz (error = 7 hz)

f) wavelength = (speed of sound)/(frequency of wave) = 340/118 = 2.9 m (error = 0.19 m)\

g) Amplitude = ((max wave height) - (min wave height))/2 = (3.5 - 1.8)/2 = 0.85 (arbitrary units of pressure)

h) increase the collections period to 0.3 seconds

Graph # 1h

This is a graph of the same group member's voice over a period of 0.3 seconds

The only part of the wave that seems to change is the amplitude. The wave appears to oscillate about 36 times in 0.3 seconds. This gives us roughly the same period, frequency, and wavelength as in the last trial. The amplitude did decrease to about 0.25, however, this is most likely due to a change in the volume of the student's voice or the distance to the microphone.

Graph #2

This is a graph of another group member speaking into the microphone.

a) # of waves = 4

b) frequency = (#of waves)/(time elapsed) = 133 hz (error = 7 hz)

c) Period = 1/frequency = 0.0075 s (error = 0.0004 s)

d) amplitude = 0.075 (arbitrary units of pressure)

e) wavelength = 2.56 m (error = 0.13 m)

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Graph #3

This is a graph of a tuning fork after striking a soft object collected over 0.03 seconds

a) # of waves = 7.5

b) frequency = (# of waves)/(time elapsed) = 7.5/0.03 = 250 hz (error = 10 hz)

c) period = 1/frequency = 0.004 s (error = 0.0002 s)

d) amplitude = 0.1 (arbitrary units of pressure)

e) wavelength = 340/250 = 1.36 m (error = 0.06 m)

waves made by the tuning fork appeared to be simple harmonic waves whereas the human voice waves were the superposition of several different sinusoidal waves.

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Graph #4

This is a graph of the same tuning fork striking a soft object and being slightly muted over a collection period of 0.03 seconds

a) # of waves = 7.5

b) frequency of waves = 250 hz (error = 10 hz)

c) Period of wave = 0.004 s (error = 0.0002 s)

d) Amplitude = 0.02 (arbitrary units of pressure)

e) wavelength = 1.36 m (error = 0.06 m)

this wave was nearly identical to the wave shown in graph #3. The only difference was that the amplitude of this wave was much less than that of the previously collected wave.