Activity

					Research Beat Frequency
Beat Frequency (pg. 505-6)

Describe how are beats are created? Draw a picture of sound wave containing beats.




Homework:
pg. 507 #1




1.   A tuning fork having a frequency of 256 Hz is sounded together with a note produced by an acoustic guitar. If the beat
     frequency heard is 3 Hz, what are the possible frequencies produced by the guitar?




2. Two tuning forks having frequencies of 256 Hz and 254 Hz are sounded at the same time. What beat frequency will be
heard?




3. A third fork of unknown frequency is sounded in turn with each of the forks in the question above. What is the frequency
of this fork if (a) 8 beats are heard in 8 s with each fork, (b) 8 beats are heard in 8 s with the 254 Hz fork and 24 beats are
heard in 8 s with the 256 Hz fork?




Answers: 1. 253 Hz, 259 Hz, 2. 2 Hz, 3. a) 255 Hz, b) 253 Hz
Activity The Oscilloscope
This is a class (group) activity.

A loud tuning fork                                 A soft tuning fork




                                                       sound pressure
    sound pressure




                                            time                                     time



A high-pitched tuning fork                         A low-pitched tuning fork




                                                        sound pressure
     sound pressure




                                            time                                     time




Two forks with slightly different pitches          Two forks, one an octave higher
                                                           sound pressure
        sound pressure




                                            time                                     time




A person’s normal speaking voice                   Noise
                                                           sound pressure
       sound pressure




                                            time                                     time



A tap at one end of the tube                       Musical Instrument 1
                                                       sound pressure
    sound pressure




                                            time                                     time



Musical Instrument 2                               Musical Instrument 3
                                                          sound pressure
       sound pressure




                                            time                                     time

				
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