Microphone

Microphone
Using the Microphone with TI Graphing Calculators
Microphone
(Order Code MCA-BTA)
The Microphone can be used for a variety of
activities with sound waves:
• Demonstrate how the wave pattern changes when frequency and amplitude
are changed
• Compare the waveforms from various musical instruments
• Have students capture the waveform of the sound of a tuning fork and
model the sine wave using a function
• Measure the speed of sound by using reflected sound waves in a tube
• Demonstrate beat patterns
• Determine the period and then the frequency of a sound by measuring the
time between peaks on the waveform
• Display the fast Fourier transform (FFT) of a sound
NOTE: This product is to be used for educational purposes only. It is not
appropriate for industrial, medical, research, or commercial applications.
Using the Microphone with a Computer
Sound ( Pressure)
This sensor can be used with a computer and either a Vernier LabPro® or a Universal
Lab Interface. Here is the general procedure to follow when using the Microphone
with a computer:
1. Connect the Microphone to the appropriate port on the interface.
2. Start the Logger Pro® software.
3. The program will automatically identify the Microphone, and you are ready to
collect data1 Here are some sample graphs made using this microphone and a
computer interface:
263-Hz Flute Sound
256-Hz Trumpet Sound
Beat Pattern
Using the Microphone with a Palm OS device
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100
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60
-20
1. Connect the Palm OS handheld, LabPro, and the Microphone.
2. Start Data Pro.
3. Tap New, or choose New from the Data Pro menu. Tap New again. The
Microphone will be identified automatically.3
4. You are now ready to collect data.
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Sound (Pressure)
-60
20
-100
0
0
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10
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Time ( ms)
amp(Pressure)
This sensor can be used with a TI graphing calculator and any of the following lab
interfaces: LabPro, CBL 2™, or original CBL™. Here is the general procedure to
follow when using the Microphone with a graphing calculator:
1. Load a data-collection program onto your calculator:
• LabPro or CBL 2–Use the DataMate program. This program can be
transferred directly from LabPro or CBL 2 to the TI graphing calculator.
Use the calculator-to-calculator link cable to connect the two devices. Put
the calculator into the Receive mode, and then press the Transfer button on
the interface.
• Original CBL–Use the PHYSICS program. This program is available free on
our web site at www.vernier.com. Our programs can also be obtained on
disk. (Contact us for more information.) Load the program into a calculator
using TI-GRAPH LINK™ or TI Connect software.
2. Use the calculator-to-calculator link cable to connect the interface to the
TI graphing calculator using the I/O ports located on each unit. Be sure to push
both plugs in firmly.
3. Connect the Microphone to any of the analog ports on the interface. In most
cases, Channel 1 is used.
4. Start the data-collection program. The Microphone will be identified
automatically.2
5. You are now ready to collect data.
Here are some sample calculator screens made using the Microphone:
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-20
-40
1 28 bins at 26 .4 Hz/ bin : peak at 1 4 24 Hz
-60
-80
-100
0
10
20
30
40
50
Time ( ms)
2 6.4
FFT of Sound ( Dat a A)
3 37 5
Sound Beat Pattern
256 Hz Trumpet
1
If your system does not support auto-ID, open an experiment file in Logger Pro, and you are
ready to collect data.
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If your system does not support auto-ID, choose SETUP and set up an experiment.
If your sensor does not auto-ID, tap Setup and set up an experiment.
2
Specifications
Frequency range: approximately 20 Hz to 16,000 Hz, but note that the maximum
data collection rate of the interface affects the maximum frequency you can
effectively sample. With the LabPro or CBL 2, the maximum sound source is
5,000 Hz. With the CBL or ULI, the maximum sound source is 1,000 Hz.
Power: 7.5 mA @ 5 VDC
Stored Calibrations
Slope = 1
Intercept = 0 (arbitrary units)
This sensor is equipped with circuitry that supports auto-ID. When used with
LabPro or CBL 2, the data-collection software identifies the sensor and uses predefined parameters to configure an experiment appropriate to the recognized sensor.
This greatly simplifies the setup procedures for many experiments. Auto-ID is
required for the Quick Setup feature of LabPro and CBL 2 when the unit operates
remotely from the computer or calculator.
How the Microphone Works
The Microphone uses an electret microphone that has a frequency response covering
essentially the range of the human ear. An op-amp circuit amplifies the signal and
sends it to the British Telecom connector. Actually the signal is sent to the interface
on two different lines. A signal centered at 2.5 volts is on the Vin-low line and a
signal centered at 0 volts is on Vin. More information about the input lines on
LabPro is available in the LabPro Technical Reference Manual.
The best sound sources to use with the microphone are tuning forks, but you may
want to investigate a human voice or a whistle, electronic keyboards, and other
musical instruments. Try comparing the wave pattern for different sound sources.
Try playing two sounds of nearly the same frequency to produce beat patterns.
Make sure the sound level is in the correct range to produce good wave patterns. If
the sound is too loud, the wave pattern will be “clipped off” at the top or bottom.
Move the microphone further from the sound source, or turn down the volume of the
sound.
Warranty
Vernier warrants this product to be free from defects in materials and workmanship
for a period of five years from the date of shipment to the customer. This warranty
does not cover damage to the product caused by abuse or improper use.
Vernier Software & Technology
13979 S.W. Millikan Way • Beaverton, OR 97005-2886
Toll Free (888) 837-6437 • (503) 277-2299 • FAX (503) 277-2440
info@vernier.com • www.vernier.com
Rev. 10/26/05
Logger Pro, Vernier LabPro, and other marks shown are our registered trademarks in the United States.
CBL 2 and CBL, TI-GRAPH LINK, and TI Connect are trademarks of Texas Instruments.
All other marks not owned by us that appear herein are the property of their respective owners, who may or may not be
affiliated with, connected to, or sponsored by us.
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