The frequency of the lower note for the two notes which plays thirty beats in one minute when played together is 739.5 Hz.
Frequency of wave is the number of waves, which is passed thorough a particular point at a unit time.
When two sound waves having different values of their frequencies, approaches to ears, then the difference of these two frequency is known as beat frequency.
Thirty beats are heard in one minute when two notes are played together. As it is known that there is total 60 seconds in one minute. Hence, the number of beats heard in one second is,
[tex]f_b=\dfrac{30}{60}\\f_b=\dfrac{1}{2}\rm beats/sec\\f_b=\dfrac{1}{2}Hz[/tex]
The higher note has a frequency of 740 Hz. The beat frequency is the difference of both the frequency. Thus,
[tex]f_b=f_h-f_l[/tex]
Put the values as,
[tex]\dfrac{1}{2}=740-f_l\\f_l=740-\dfrac{1}{2}\\f_l=739.5\rm Hz[/tex]
Hence, the frequency of the lower note for the two notes which plays thirty beats in one minute when played together is 739.5 Hz.
Learn more about the beat frequency here;
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