Physics 2225 Minilab 1: A Look at Sound

Purpose

• Visualize the wavelike nature of sound by using a sound-to-voltage transducer (otherwise known as a microphone….).

• Measure the speed of sound in a variety of ways.

Physics 2225 Minilab 1: A Look at Sound

Activity I: The Nature of Sound

Sound

Microphone (converts sound to electric voltage)

Pasco 750 Interface

Computer/Data Studio : Used as an oscilloscope

Physics 2225 Minilab 1: A Look at Sound

Data Studio as a 1-Channel Oscilloscope

adjust horizontal axis by clicking on black triangles

adjust vertical axis by clicking on black triangles

adjust trigger level here by sliding triangleup or down

Physics 2225 Minilab 1: A Look at Sound

T (period)

Tf

1

divms11ms

Physics 2225 Minilab 1: A Look at Sound

Activity II: Standing Waves and the Speed of Sound

tuning fork

Procedure: Adjust pipe location until the sound from the

tuning fork is amplified. Measure L as shown on the left. Think about the relationship between the

wavelength and the length L. Determine wavelength Calculate the speed of sound using

L

fvs

Note: f is written on the tuning fork.

Physics 2225 Minilab 1: A Look at Sound

Review: Uncertainty from Repeated Measurements (e.g., Q8)

Calculate the average speed of sound from several measurements.

Determine the standard deviation v

Calculate the standard deviation of the mean:

)tsmeasuremen ofnumber theis N(

Nv

v

v

vv Result

Physics 2225 Minilab 1: A Look at Sound

Activity III: Measuring the Speed of Sound with Microphones

table

stand

Microphone 2 (plugged into port B !!)

Microphone 1 (plugged into port A !!)

Clap !

d

t

dv

time

distance

Physics 2225 Minilab 1: A Look at Sound

How We Measure “t”

The basic idea:

Sound first hits microphone 1 Triggers the oscilloscope

Measurements on both microphones are started simultaneously and displayed in Data Studio (acts now as a 2-Channel oscilloscope).

Sound pattern is seen on Channel A first, then Channel B.

Time shift in sound pattern (Ch A versus Ch B) is “t”.

Physics 2225 Minilab 1: A Look at Sound

Data Studio as a 2-Channel Oscilloscope

adjust horizontal axis to 0.5 ms/div

adjust vertical axis ofChannel A or B.Make Ch. A 5 Volts/divMake Ch. B 2 Volts/div

Suggested values:Please play withthese adjustmentsas needed.

Physics 2225 Minilab 1: A Look at Sound

After a Successful Clap … Identify Repeat Pattern

t

It may require severalclap attempts beforeyou can reliablyrecognize thesame pattern inChannel B as inChannel A.

Physics 2225 Minilab 1: A Look at Sound

Activity IV: Measuring the Speed of Sound with an Echo

Table

Stand

Microphone 1 (plugged into port A !!)

Clap !

dt

dv

2

time

distance

Hollow cardboard tube

Physics 2225 Minilab 1: A Look at Sound

First passage

Echo

Identify a repeated pattern…you may need several attempts

t

Physics 2225 Minilab 1: A Look at Sound

% Difference (e.g., Q 13)

100%

valueltheoretica

valueltheoreticavaluemeasureddifference

Physics 2225 Minilab 1: A Look at Sound

Important

In the lab manual the data studio activities are called: “Sound1.ds”, “Sound2.ds”, “Sound3.ds”

The actual files are called:“A Look at Sound 1.ds” ….etc…

Whenever you launch a new Data Studio file, you must first close all other existing Data Studio files. Then launch the new one. Still, sometimes the “Start Button” won’t work. If that happens, close the file and launch it again.