Sound

The names of two musical instruments are veena and flute.

The vibrating parts of Veena and flute are stretched string and air column respectively.

Two musical instruments which produce sound by simple beaten are manjira and ghatam.

The part of the body which produces sound is the voice box or larynx.

The position of muscles of vocal cord when we are not speaking is loose and relaxed.

No, sound cannot travel without medium.

If sharp or pointed things are put into the ear it can damage the eardrum inside our ear. This can make us deaf.

In toy telephone the sound travels through the string i.e. a solid medium.

The SI unit in which the loudness of sound is measured is decibel (dB).

The time period (T) and the frequency (f) are inversely proportional to each other

The shrillness of sound is the characteristic property of sound which differentiates the sound between male and female. Usually, the voice of a woman has higher frequency and shriller than the voice of a man.

The range of audible sound is from 20 Hz to 20000 Hz or 20 kHz.

The reason behind the creation of noise is vibrating objects.

Planting trees along roadside is helpful because

1. Plants reduce noise pollution.

2. Plants reduce air pollution.

Hearing impairment is the hearing defect of a person. Total hearing impairment is a problem usually from birth but partial hearing impairment is caused due to age, injury or illness.

A sound making object is a vibrating object for which it can produce sound while a silent body is a non vibrating object.

As a fire cracker explodes it produces a vibration in the air medium around it which is the reason we can hear a fire cracker exploding.

The name of passage in the outer ear which carries sound waves to the eardrum is ear canal.

no, sound cannot travel through vacuum as for propagation of sound it needs a medium.

Amplitude is defined as the loudness of sound. When the amplitude is large the sound produced is large and if the amplitude is small then the sound produced is also small.

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

Sound of loudness lower than 80 dB can be tolerated by a normal human being.

Manjira consists of two metal discs that when struck against each other produces sound. When the two metal discs are struck against each other they vibrate and produce sound.

Infrasonic sound is the sound with frequency lower than 20Hz but ultrasonic sound is the sound with frequency higher than 20000Hz or 20 kHz.

Sound propagates fastest in solid medium, so the sound of an approaching train can be heard even when the train is far off.

Thunder is heard after lighting because lights travels much faster (3 x 10⁸ m/s) than sound (about 330 m/s).

The shrillness of sound is the characteristic property of sound which differentiates the sound between male and female. Usually the voice of a woman has higher frequency and shriller than the voice of a man.

Musical sounds are those sounds which are pleasing to the ear while noise is those sounds which are unpleasant to the ear.

Some harmful effects of noise pollution are:

1. Lack of sleep

2. Hypertension

3. Anxiety

4. Temporary or even permanent loss of hearing.

Fig. Labelled diagram of larynx

The larynx or the voice box produces sound. Two vocal cords are stretched across the larynx while leaving a small slit between them for the passage of air. When the lungs force air through the slit, the vocal cord vibrates and produces sound. The muscles attached to the vocal cord can make it tight or loose, if it is tight the sound produced is of high frequency and if it is loose then the sound produced is of low frequency.

Fig. Labelled diagram of an ear

When the sound vibrations fall on the funnel shaped outer ear, the vibrations are transmitted through the ear canal to the eardrum which is a rubber membrane and vibrates when sound vibrations fall on it. Then the vibration goes to the inner ear from which it goes to the brain. This is how we hear.

When the vocal cord is

a) tight and thin: the sound produced is of high frequency or it is of high pitch.

b) loose and thick: the sound produced is of low frequency or low pitch.

When we prick a stretched rubber band, we can see the to and fro motion of the rubber band. This motion of the rubber band is known as vibration.

When the rubber band is vibrating, the number of small oscillating loops that the rubber band makes is defined as the frequency of the rubber band. The more the oscillating loops more is the frequency of the rubber band and vice versa.

Toy telephone works due to sounds produced by vibration of stretched wire. Toy telephone is a basic telephone made out of a long string and two paper or plastic cups. When a person speaks at one of the cups then the vibrations of sound produced by the stretched wire enables the other person to hear his voice successfully. Hence, we can conclude that sound produced by stretched wire is due to vibration.