PHY 140 Lab 5
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CUNY Lehman College *
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Course
140
Subject
Industrial Engineering
Date
Dec 6, 2023
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4
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Lab #5: Sound Intensity- The Decibel Scale
Danisha Rincon
04/12/2022
Lab section: Tuesdays, 6:15 - 7:45 pm
Experiment 5
SOUND INTENSITY - THE DECIBEL SCALE
PURPOSE
This laboratory was conducted with the purpose To understand the decibel scale in measuring
sound intensities. The level for frequencies and sound intensity level are factors being calculated
and analyzed in this experiment. Sound source, two loudspeakers, sound level meter and
scientific calculator are the objects being used to do the experiment part of the lab while the
formulas provided with the theory were used to process the mathematical part of the lab. The
experiment was conducted with classmates and the data was collected through a series of trials
using the materials.After recording the measurements from the formulas provided were used to
confirm the data and also to compare the theoretical to the result.
APPARATUS:
Sound source
Two loudspeakers
Sound level meter
Scientific calculator
THEORY
The human ear on average can detect sounds with an intensity as low as 10
−
12
W/m
2
and as high as 1
W/m
2
(and even higher, although above this it is painful).
This is an incredibly wide range of intensity, spanning a factor of a trillion (10
12
)
from lowest to highest. Presumably because of this wide range, what we
perceive as loudness is not directly proportional to the intensity. The human ear
responds
logarithmically
to sound, which means that the intensity scale is
compressed so that distances between the endpoints are not so large. To produce
a sound that sounds twice as loud requires a sound wave that has about 10 times
the intensity; a sound that sounds three times as loud requires a sound wave that
has 100 times the intensity and so on.
PROCEDURE
In this lab, two speakers will be used to produce sound. You will measure the sound
intensity level in dB with a sound level meter for each speaker separately and then for both
speakers together at different points in the room.
1. Take a station in the room. Be very quiet. When the first speaker is turned on, record the
intensity in dB. Do the same when the other speaker is turned on. Next record the
combined intensity when both speakers are turned on. Fill in the Table 1 below.
2. Move to the next station and repeat the experiment until your table is complete.
DATA
Table 1
Station
SIL 1
(dB)
SIL 2
(dB)
Combined
SIL (dB)
1
60.4
53.5
62.6
2
68.7
64.2
66.1
3
69.1
59.4
67.4
4
61.5
64.0
68.0
5
63.3
55.8
64.3
ANALYSIS
1) Convert the decibel readings in Table 1 into
W/m
2
using the formula given in the
theory section. Fill in table 2 below.
2) The combined intensity in
W/m2 should
be the sum of the two individual
intensities. Do your measurements agree with this? Compare the last two columns in
table 2. Comment.
Table 2
Station
intensity
1 (
W/m
2
)
intensity
2 (
W/m
2
)
Combined intensity
(
W/m
2
)
intensity 1 +
intensity 2 (
W/m
2
)
1
0.0000010
965
0.0000002
238721138
(0.0000010965) +
(0.0000002238721138)
= 0.00000132 W/m2
61.2 dB
2
0.0000074
131
0.0000026
303
(0.0000026303)+(0.000
0074131)=0.000010043
4 W/m2
70.1 dB
3
0.0000081
0.0000008
0.0000081283+0.00000
69.5
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283
709635899
08709635899=0.00000
899926 W/m2
4
0.0000014
125
0.0000025
119
0.0000025119+
0.0000014125
=0.0000039245 W/m2
65.9 dB
5
0.0000021
38
0.0000003
801893963
0.0000003801893963 +
0.000002138=0.000002
51818 W/m2
64.0 dB
To conclude , the laboratory shows that what we perceive as loudness is not directly proportional
to the intensity. However, the experiment did not meet the theoretical expectation because when
the number were converted they weren’t equal yet they were very close, leading to believe that it
could’ve been human errors that didn’t give the result expected.