Sound intensity levels lab report

OBJECTIVE

The purpose of this experiment is to:

1. 1) measure sound intensity levels (SIL) in decibels (dB) and verify that an increase in SIL, eg. when
   two sources are played simultaneously, are a result of adding individual intensities (in W/m2),
   and not by adding the SILs directly.
2. 2) establish a relationship between SIL (dB) and distance (m).

METHOD

Two sound sources of the same frequency are played individually, and then simultaneously, while the
SIL (dB) are measured using calibrated sound level meters (SLMs) tuned to the A-weighting setting. The
A-weighting setting sets a filter on the SLMs to make them mimic the characteristics of the human ear.

Data is gathered on a table, suggested by Table 1 below.

Table 1: Suggested table for gathering the data

ANALYSIS

1. 1) Generate a new table, converting all the SIL (dB) from Table 1 to intensity (W/m2), and call this
   Table 2 from this point forward. A suggested format for Table 2 is shown below.
2. 2) Add the intensities for source A and for source B along the same locations, and put the values on
   an additional column on Table 2. This will be the theoretical (or accepted value) for calculating
   the error in this experiment.
3. 3) Calculate the error in your experimental value for intensity IA+B (dB), using IA + IB (dB) as the
   accepted value, and record them on the last column of Table 2.
   Table 2: Suggested table for Analysis
4. 4) Plot a graph of SIL (dB) vs. distance (m) for source A, and another one for source B. (You may
   have a hard time drawing both on the same axes, so it’s okay to have 2 separate graphs). Try to
   draw a smooth curve joining the points on both graphs.
5. 5) What is the trend that is seen in both graphs as distance from the source increases?

2

1. 6) Theoretically, what happens to the intensity (W/m2) of a sound when the distance is doubled?
2. 7) Theoretically, what happens to the SIL (dB) of a sound when the distance is doubled?
3. 8) a) From your first graph of SIL (dB) vs distance (m) for source A, calculate the change in the SIL
   (dB) for source A as the distance doubles from r = 2 m to r = 4 m.
   b) From your second graph of SIL (dB) vs distance (m) for source B, calculate the change in the
   SIL (dB) for source B as the distance doubles from r = 3 m to r = 6 m. You will have to estimate
   the values of the SIL (dB) at r = 3 m and r = 6 m from the graph after you have drawn a smooth
   curve joining the points.
4. 9) Do these estimates of the change in SIL (dB) values match with the theoretical predictions
   drawn in Q #7 above?
5. 10) Suggest the sources of error in this experiment (do not write “human error”!), any precautions
   that can be taken, and any improvements that can be made to reduce the errors while taking the
   measurements.

table has been completed for the sound intensity levels, i will attach, please graph the points.