Learning Forum

[Keyur Kanade]

Hi! I read that human ear can hear sounds in the range of 20 to 20000 Hz. What does that mean? What is a Hz? 

[Karthik Remella]

Hi @kkanade

Hz is short for Hertz, which is a unit used to measure frequency. Frequency of a sound wave (or any wave for that matter) is the number of cycles of periodic motion occurring over a unit time. 1Hz means that the wave completes 1 full oscillation in 1 second of time. So human hear can perceive sound waves that complete between 20 to 20000 cycles per second of time.

[Keyur Kanade]

Thanks for the answer @Kremella . So if someone talks at a very low volume, I am unable to hear it because they are talking at a vey low frequency. Right? So as the distance between the person and myself reduces, the frequency of the sound increases and that is why eventually I am able to hear them?

[prajput]

No, the loudness of a sound is determined by its amplitude. Amplitude is the maximum displacement of a vibrating body (air particles through which sound waves are propagating in this case) from its equilibrium position. For a human ear to perceive a sound, the frequency of the sound wave has to be between 20 to 20000 Hz, AND its amplitude should be large enough. In this case, reducing the distance between you and the person increases the amplitude of the sound and hence it becomes louder due to which you can hear it. The frequency of the sound remains unchanged by the distance.

[Karthik Remella]

To add to the above answer, the frequency of a sound-wave determines its pitch, while amplitude of the sound-wave determines its loudness.