Unformatted text preview:

Phy 103: Fundamentals of Physics III 1Instructor: Tony ZableExperiment: Sound Waves and BeatsOBJECTIVESo Measure the frequency and period of sound waves produced by a keyboard.o Measure the amplitude of sound waves produced by a keyboard.o Observe beats between the sound waves of two notes produced by a keyboard.MATERIALSo Windows PC o Logger Proo LabPro Interface o Electronic keyboard or (2 tuning forks)o Vernier MicrophonePRELIMINARY QUESTIONS1. Why are instruments tuned before being played as a group? In which ways do musicians tune their instruments?2. Given that sound waves consist of series of air pressure increases and decreases, what would happen if an air pressure increase from one sound wave was located at the same place and time as a pressure decrease from another of the same amplitude?PROCEDURE1. Connect the Vernier Microphone to CH 1 of the LabPro Interface. 2. Prepare the computer for data collection by opening “Exp 21” from the Physics with Computers experiment files of Logger Pro. The computer will take data for just 0.05 s to display the rapid pressure variations of sound waves. The vertical axis corresponds to the variation in air pressure and the units are arbitrary.Part I Simple Waveforms 1. Produce a sound with a keyboard, hold it close to the Microphone and click . Thedata should be sinusoidal in form, similar to the sample on the front page of this lab. Try choosing different instrument setting until you find a smooth waveform.2. Note the appearance of the graph. Count and record the number of complete cycles shown after the first peak in your data.3. Click the Examine button, . Drag the mouse across the graph and record the times for the first and last peaks of the waveform. Divide the difference, Dt, by the number of cycles to determine the period of the keyboard.4. Calculate the frequency of the keyboard sound in Hz and record it in your data table.5. Drag the mouse across the graph and select the “Statistics” button. Record the maximum and minimum y values for an adjacent peak and trough.File: Ph103_Lab2_beats.docPhy 103: Fundamentals of Physics III 2Instructor: Tony Zable6. Calculate the amplitude of the wave by taking half of the difference between the maximum and minimum y values. Record the values in your data table and print your graph (only one graph for your group).7. Save your data by choosing Store Latest Run from the Data menu. Hide the run by choosing Hide Run Run 1 from the Data menu. 8. Repeat Steps 1 – 7 for the second frequency (key). Store the latest run. It will be stored as Run 2. Then hide Run 2.DATA TABLE (PART I SIMPLE WAVEFORMS)KeyboardnoteNumberof cyclesFirstmaximum(s)Lastmaximum(s)t(s)Period(s) Calculatedfrequency(Hz)Keyboardnote Peak(pressure)Trough(pressure)Amplitude(pressure)Part II Beats1. Collect data while the two tones are sounding simultaneously. You should see a time variation of the sound amplitude. When you get a clear waveform, choose Store Latest Run from the Data menu. The beat waveform will be stored as Run 3.2. The pattern will be complex, with a slower variation of amplitude on top of a more rapid variation. Ignoring the more rapid variation and concentrating in the overall pattern, count the number of wave packets, beginning at the first discernible node, and record it in the data table.3. Click the Examine button, . Drag the mouse across the graph and record the time for the first and last node on the display. Divide the time difference between the first and last node, Dt, by the number of beats to determine the period of the beats (in s). Calculate the beat frequency in Hz from the beat period. Record these values in your data table.DATA TABLE (PART II BEATS)Number ofbeatsFirstmaximum(s)Lastmaximum(s)t(s)Beat Period(s)Calculated beatfrequency (Hz)File: Ph103_Lab2_beats.docPhy 103: Fundamentals of Physics III 3Instructor: Tony ZableQuestions:1. How can the two individual frequencies can be related to give the beat frequency you measured above? Compare your conclusion with information given in your textbook (or lecture notes).2. (Time Permitting) Examine the beat pattern you get when you play two adjacent notes on a keyboard. How does this change as the two notes played get further and further apart? How does it stay the same?3. Why do the beats produced by 2 sound waves appear more noticeable as the frequencies of the waves get closer together?File:


View Full Document

PCC PHY 103 - Sound Waves and Beats

Download Sound Waves and Beats
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Sound Waves and Beats and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Sound Waves and Beats 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?