Question

Anyone has class 9th science project​

Answer 1

Answer:

Activity: To identify pitch of a sound

1. Take two hack-saw blades or metal

scales of 30 cm length and a brick.

2. Place the first blade/scale on the

table such that 10 cm portion is on

the table and 20 cm portion is in air.

3. Place the second blade/scale on the

table with 25 cm portion on the

table and 5 cm portion in air.

4. See that the gap between two

blades is 10 cm and place the brick

(as weight) on the scales.

5. Vibrate both blades with same

force. Observe the vibrations and hear the sounds produced.

6. We observe that the number of vibrations produced is less in first blade/scale when

compared to the second blade/scale.

7. The sound produced by the second blade/scale is shriller when compared to the sound

produced by the first blade/scale.

MUSIC AND NOISE:

Music: The sound which is pleasant to hear is called MUSIC.

Example: Sounds produced by musical instruments.

Noise: The sound which is unpleasant to hear is called NOISE.

Example: Irregular sounds produced in a class-room by the students.

AUDIBLE RANGE OF HUMAN BEINGS:

Note: The number of vibrations per second is called FREQUENCY.

1. The sounds that a normal human being can hear are called AUDIBLE SOUNDS.

2. The frequency of the audible sound ranges from 20 vibrations/second to 20000

vibrations/second.

3. The frequency of inaudible sounds is less than 20 vibrations/second or more than

20000 vibrations/seconCHARACTERISTICS OF SOUND:

Loudness: The degree of the sensation produced on the ear is known as LOUDNESS of

sound. It is expressed in decibels (dB).

Example: Sound produced from drums in the school assembly.

Feebleness: The lack of volume or loudness is known as FEEBLENESS of sound.

Example: Sound produced while taking pledge in the school assembly.

Loudness and feebleness of a sound are measured in decibels(dB)

Amplitude: The maximum displacement of a vibrating body from its mean position is

known as AMPLITUDE.

Loudness and feebleness of a sound depend on AMPLITUDE of vibration.

Pitch: The Shrillness of a sound is known as PITCH.

Explanation:

1. thanks my answer......