# Properties of Sound

Sound is vibration; we can represent sound using a diagram, a shape like a mountain and a valley. Sound is measured in Hertz.

The sounds’ speed varies depending on some parameters, so it is not constant, and it changes according to

• Temperature
• Medium of travel (solid, liquid, gas)
• Humidity of air

Sound Frequency:

The vibrations in every sound are called Frequency, the waves number in one second.

For example, if ten waves are complete in one second, then the Frequency of the sound is 10 Hz (Hertz).

#### What Is the Speed of Sound?

The distance travelled by sound per unit of time through the medium is called the speed of sound.

Speed of Sound Formula:

We know that,

Speed= Distance/Time

Speed= Distance*1/Time

In the case of the sound wave,

Distance = Wavelength

and

DistanceTime =Frequency
Also,Time= 1Frequency

So, the formula for the speed of sound becomes,

Speed = Wavelength * Frequency

From this formula, we can say that,

Wavelength= Speed*Frequency

and Frequency

SpeedWavelength

Sound requires a medium to travel.

Example:

• The sounds’ speed in the air is 346 m/s.
• The sounds’ speed in water is 1531 m/s.
• The speed of sound in iron is 5950 m/s

Hearing Range:

Sonic Sound In this range, the sound frequency lies in the field of 20 Hz to 20,000 Hz. It is the human hearing range.

Infrasonic Sound In this range, the sound frequency is less than 20 Hz.

Ultrasonic Sound The sound frequency is greater than 20,000 Hz in this range.

Hearing Range Table:

Organism Hearing Range
Human being 20-20,000
Elephant 16-12,000
Cow 23-35,000
Rat 200-76,000
Bat 2,000-110,000
Horse 55-33,500
Dog 67-45,000
Rabbit 360-42,000

As humans grow, their hearing also changes:

• Childhood: 15 Hz - 15,000 Hz
• Adult age: 20 Hz - 20,000 Hz
• Old age: 50 Hz - 8,000 Hz
• Most sensitive range: 1,000 Hz - 4,000 Hz