Post on 13-Jan-2016
transcript
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.