High School Physics

# Sound characteristics | Features of sound

All sounds that you hear are not the same. There are some properties that differentiate one kind of sound from another. We will study about these Sound characteristics or features now. We will study about loudness, pitch, quality, and audibility (& range) of sound.

Loudness

Loudness is defined as the characteristic of a sound that enables us to distinguish a weak or feeble sound from a loud sound.

The loudness of a sound depends on its amplitude.

The higher the amplitude louder will be the sound and vice versa.

When a drum is softly beaten, a weak sound is produced. However, when it is beaten strongly, a loud sound is produced.

The unit of the loudness of sound is the decibel (dB).

Pitch

The pitch is the characteristic of sound that enables us to distinguish between a flat sound and a shrill sound.

The higher the frequency of sound, the higher will be the pitch.

High pitch adds shrillness to a sound. The sound produced by a whistle, a bell, a flute, and a violin are high
pitch sounds.

Normally, the voice of a female has a higher pitch than a male. That is why a female’s voice is shriller than a male’s voice. Some examples of low-pitch sounds are the roar of a lion and the beating of a drum.

Quality or Timbre

The quality or timbre is the characteristic of sound that enables us to distinguish between two sounds that have the same pitch and amplitude.

For example in an orchestra, the sounds produced by some musical instruments may have the same pitch and loudness. Yet, you can distinctly identify the sound produced by each instrument.

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Audibility and Range

According to the frequency, we can classify the sound into three types. They are:

• Audible sound
• Infrasonic sound
• Ultrasonic sound

Sound with frequency ranging from 20 Hz to 20000 Hz is called sonic sound or audible sound. Human ears cannot hear sounds with frequencies below 20 Hz or above 20000 Hz. So, the above range is called the audible range of sound for human beings.

A sound with a frequency below 20 Hz is called a subsonic or infrasonic sound. Humans cannot hear the sound of this frequency, but some animals like dogs, dolphins, etc., can hear.
Uses of infrasonic sound are given below.

• It is employed in the Earth monitoring system.
• It is also used in the study of the mechanism of the human heart.

A sound with a frequency greater than 20000 Hz is called ultrasonic sound. Animals such as bats, dogs, dolphins, etc., are able to hear certain ultrasonic sounds as well. Some of the uses of ultrasonic sounds are given below.

• It is extensively used in medical applications like ‘Sonogram’.
• It is used in the SONAR system to detect the depth of the sea and to detect enemy submarines.

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