1) Use a sound level meter or an app to measure the following: a) Conversational

Question

1) Use a sound level meter or an app to measure the following:

                a) Conversational intensity of one of your group members (within three feet).

                b) Ambient noise in the classroom.

                c) Intensity of the instructor or someone across the room (at least 10 feet away).

2) Compare the intensity of a speaker at various distances from your measurement tool.

3) What happens to the decibel level as we move further from the source of the sound?

How does this relate to the inverse square law?

Explanation / Answer

(1)A sound level meter is used for acoustic (sound that travels through air) measurements. It is commonly a hand-held instrument with a microphone. The diaphrahm of the microphone responds to changes in air pressure caused by sound waves. That is why the instrument is sometimes referred to as a Sound Pressure Level (SPL) Meter. This movement of the diaphrahm, i.e. the sound pressure deviation (pascal Pa), is converted into an electrical signal (volts V).

(2) Sound intensity decrease with distance to source. Sound intensity vs. distance can be expressed:

I = Lw / 4 r2        

where

Lw = sound power (W)

= 3.14

r = radius or distance from source (m)

(3) The decible level decreases ,as we move further from the source of the sound.

The sound intensity I (energy) falls inversely proportional to the square of the
distance 1/r2 from the sound source. I ~ p2 or I2 = I1×(r1/r2)2

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