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Sound, 1., , sound is produced by the vibration of objects. Objects that produce sound are, known as the sources of sound., , 2., , Frequency = No: of oscillation/time, f = n/t, , 3., , Define natural frequency?, When a body is set into vibration, it vibrates with a particular frequency of its, own. This frequency is its natural frequency., , 4., , Difference between Pitch and loudness?, The sharpness of sound heard is its pitch., Loudness is the measure of audibility of a person. Its unit is decibel (dB)., , 5., , Complete the tables:, , 6., , Match the following [Answer], A, Sharpness of sound, Measure of audibility, Limit of audibility, Galton whistle, , B, :, :, :, :, , Pitch, Loudness, 20 – 20,000 Hz, Dog whistle [about 30,000 Hz]

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7., , Differentiate between infra & ultra-sonic sounds?, Infrasonic sounds: - Frequency less than 20 Hz. E.g. Sounds of earthquake., Ultrasonic sounds: - Frequency greater than 20000Hz (20KHz) ., E.g. Sounds made by bats, SONAR etc., , 8., , Mention 3 methods to reduce noise pollution., o Ensure use of proper silencer in vehicles., o Avoid using airhorns and loudspeakers., o Plant trees., , ‘Let us assess’ answers., 1., , 480Hz, , 2., , 1 Hz, , 3., , Nature of material, length, area, tension., , 4., , Highest Pitch..512Hz, Lowest Pitch ..256 Hz, , 5, , a. Diaphragm, b. Air column, c. Larynx, , 6., , Make a toy telephone using 2 matchboxes. Connect them through a thread., Speak into one matchbox. Then sound travels through this thread and a person, holding the other match box can hear the sound., , 7., , a. True, b. False. When frequency increases, pitch also increases, , 8., , Yes. Bats make use of ultrasonic sound., , 9., , Airhorn, loud sound of vehicles, sound of machines etc., , 10., , dB., , 