Name: Speed of Sound Waves in Solids and Liquids
Uploaded: 2019-07-19
Duration: 6 min 40 s
Description: This video enables students to understand the dependence of the speed of sound on the medium properties like young modulus or bulk modulus and density.

Question

You can probably hear notes of higher pitch than your teacher. Describe how you would show this in the school laboratory.

Accepted Answer

Pitch is the characteristic of sound which distinguishes between a shrill sound and a growling sound. The pitch of a sound depends on the frequency of the sound wave. The greater the frequency, the higher the pitch. The number of oscillations of the density of the medium at a place per unit time is called the frequency of the sound wave. Children can hear sounds of somewhat higher frequencies, say up to $30 KHz$ . We know that with age, our ability to hear high-frequency sound diminishes. For the elders, the upper limit often falls to $10 - 12 kHz$ . Hence, an aged person may not be able to hear notes of higher pitch compared to a young person. In the laboratory experiments, sound is produced by vibrating tuning forks. A tuning fork has two hard steel prongs that are connected at the lower end to a stem or handle. When the prongs of the tuning fork are struck on a hard rubber pad, the prongs vibrate and a sound is produced. We have to take tuning forks having different frequencies (having low and high frequencies) and made them vibrate next to a microphone connected to an oscilloscope. Then the microphone receives the vibrations from the instrument and converts them to an electrical signal, which will be displayed on the oscilloscope screen. We know that if we are made to vibrate a tuning fork having frequency $256 Hz$ , it will produce sound waves having the same frequency. In this manner if we made to vibrate a tuning fork having a frequency of about $15 kHz$ , it will produce sound waves having frequency of $15 kHz$ . But only the students can hear frequency of this range, their teacher cannot hear this sound as it is above her audible range. But she can observe the high pitch signal through the oscilloscope and realise that sound is there, but she is unable to hear. Thus, with the help of tuning forks having low and high frequencies, we can show that students can hear notes of higher pitch than their teacher.

You can probably hear notes of higher pitch than your teacher. Describe how you would show this in the school laboratory.

Important Questions on Sound

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