SOUND Sound contd...

Activity 5.6

You will need: - Six tall glass tumblers of the same size, a metal spoon, water

Method: - Fill the six glass tumblers with water to varying heights as shown in the figure. Tap the edge of each tumbler with a spoon gradually, starting from the one with less water. Listen to the sound produce carefully.

A b c d e f

Observation: Glasses produce different sounds. The pitch of the sound increase from “a” to “e”.

Conclusion: Glasses with different water column height produce different sounds.

There are some other

instruments produce sounds by vibrating air column.

Observation: When each hole is open and close from opposite end to the mouth, the pitch of the sound increases gradually. We can produce different sounds when open and close different holes.

Conclusion:

Thus, flute is a musical instrument that changes the sound with the change of the length of air column vibrated. It is played with the blow of air that vibrates the air column in the flute. The air pores are closed and opened with the fingers to produce different sounds in music.

5.3 Musical instruments that produce sound by vibrating strings/rods

Observation: When the length of the wires and their tensions are changed the sound changes.

Conclusion: Frequency of the sound change with the length, tension and the width of the wire.

Observation: Thin wires produce sharp sounds than thick wires.

Short wires produce sharp sounds than long wires.

When the same wire is tighten it produce sharp sounds.

Conclusiound: A sharp (high) sound is produced when short, tight, thin wires are vibrated. Sound produced by the vibration of long, loose and thick wire is not that sharp.

When a guitar or a violin is being tuned, the length and the tension of the wires are changed.

Sound may also be changed by the way and the speed of vibrating the strings.

5.4 Musical instruments that produce sound by vibrating bars/plates

Xylophone and symbols are some instruments that have vibrating plates. Following activity(5.10) is designed to understand the factors that change the sound produce by it.

Observation: When tap on longest plate, it gives lowest sound. Sound is high when tap on shortest plate. Conclusion: The frequency is changed according to the change of the length of plates.

� Here, tapping to the shorter plates, gives higher (intense) sound than tapping to the longer plates.

� This is similar to the set of tuning forks, where shortest one gives highest sound and longest one gives lowest sound.

Prepare the simple models of musical instruments as given in the assignments and bring them to the class room when you are assign to present a group display.

Musical tones and noises

Music:

Rhythmical sounds which are pleasant to our ears are musical tones. Such sounds are produced by methodical or formal vibrations of objects.

Noises: Sounds which are unpleasant to our ears are called noises. They are produced by non-formal vibrations of objects. Noises

What types of sounds are harmful to our years? High and noisy sounds may be harmful to ears. They disturb our day-to-day activities. Even a musical tone may be unbearable to our ears, when the sound of which is very high. It depends on the relevant person. It is our duty to use instruments that produce sounds without disturbing others.

 

Ancient/traditional and musical instruments

Name some traditional musical instruments and the special occations they use.

Modern musical instruments

Special importance of modern musical instruments is that a single person can fulfil the necessity of a full orchestra or a number of instruments by using a computer and a keyboard.

Name some modern musical instruments.

Musical therapy

Music has an ability to heal the mental stress and give spiritual happiness to the people spending busy life. Training a person from his childhood to enjoy music will be helpful to develop a healthy mind. The treatment given using music is known as musical therapy. What types of diseases can use this method to improve health condition of their patients?

Patients with,

� diseases and disorders of brain and nervous system � heart failures � mental depression

Nowadays musical therapy is used in many countries of the world to coordinate muscle movements in sport activities like running and cycling to prepare patients for surgeries and as a healing method after surgeries. Can we hear a vibration of any frequency? Following activity can be use to understand this.

Observation: When the short blade is vibrating, a sound can be herd. No sound is heard though the longer blade is vibrating. Conclusion: We cannot hear the sound of any frequency. Hearing Range We can hear only the sound of a certain range of vibrations. That range we can hear is known as the limits of hearing. It is observed that different animals have different hearing ranges. The frequency of sound is measured by the unit “Hertz” (Hz)

Eg. Human: 20 Hz to 20000 Hz

Dogs: > 20 Hz

Bat: < 70000 Hz