Flash Education

Question

Give reasons for the following: (a) The reverberation time of a hall used for speeches should be very short. (b) A vibrating body produces sound. However no sound is heard when a simple pendulum oscillates in air. (c) Sounds of same loudness and pitch but produced by different musical instruments like a violin and flute are distinguishable.

Sound CBSE Class 9

CBSE, Class 9, Exam Idea, Science

August 7, 2024

Answer

(a) If the reverberation time of a hall is long, then the multiple echoes will enterfere with original sound. For this reason nothing will be heard distinctly. So, the reverberation time of the hall should be very short.

(b) A sound is heard only if the body vibrates with a frequency more than 20 Hz and less than 20,000 Hz. The pendulum oscillates with a frequency less than 20 Hz. Hence, no sound is heard.

(c) This is due to the quality or timbre of sound waves.

Was this answer helpful?

Didn't liked the above answer ?

Text Generation Tool

💡 Some Related Questions

Sound CBSE 9

Reena’s grandmother took her mother to a doctor as she was four months pregnant for ultra-sonography. But she showed her interest in determining whether the child is a boy or a girl. The doctor was annoyed and refused to disclose the gender of the child. (𝒊) What is ultra-sonography? (𝒊𝒊) Why do you think the doctor refused to determine the gender of the child? (𝒊𝒊𝒊) What values are promoted by the doctor?

Sound CBSE 9

Kunal and Abhimanyu were waiting to go across a railway crossing. Kunal jumped over the barrier and curiously put his ear on the railway track. Abhimanyu opposed Kunal and pulled him away from the railway track. (𝒊) Why did Kunal put his ear on the railway track? (𝒊𝒊) Can sound travel faster through (a) Copper (b) water. (𝒊𝒊𝒊) Why did Abhimanyu pull Kunal away from the railway track?

Sound CBSE 9

Kanika carried out an experiment on determination of speed of sound in air using resonance tube apparatus and obtained absurd results. She should (a) record the result as such. (b) manipulate the result and report the answer nearer to actual value of velocity of sound in air. (c) copy the result obtained by another student. (d) report the result as such and discuss the matter with the teacher to find out the reasons for wrong results. Answer the following questions based on the above information: (𝒊) Which is the most appropriate option for Kanika? (𝒊𝒊) What values will Kanika be promoting through preferring this option? (𝒊𝒊𝒊) Give one more example of promoting such values in real life situations.

Sound CBSE 9

What should be the minimum distance between the listener and the reflector to hear an echo of sound propagating with a speed v ms-? (b) Does the speed of sound increase or decrease on a hotter day? Justify.

Sound CBSE 9

Figure shows the position of layers of air, at one moment, as a sound wave of constant frequency passes through the air. Compressions are labelled C. Rarefactions are labelled R.
(a) State how figure would change if (i) the sound had a higher frequency, (ii) the sound were louder. (b) On figure, draw a line marked with arrows at each end to show the wavelength of the sound.

Sound CBSE 9

In a ripple tank, 12 full ripples are produced in one second. If the distance between a crest and next trough is 10 cm, find (a) wavelength, (b) frequency and (c) velocity of the wave.

Sound CBSE 9

When we put our ear to a railway track, we can hear the sound of an approaching train even when the train is far off but its sound cannot be heard through air. Why?

Sound CBSE 9

Figure shows a loudspeaker cone oscillating to produce sound waves: (𝒂) As the sound wave passes a point, it produces regions of higher and lower pressure. State the names of these regions. (𝒃) Describe how the movement of the loudspeaker cone produces these regions of different pressure. (c) State the effect on the loudness and pitch of the sound from the loudspeaker when (𝒊) the amplitude increases but the frequency of the sound stays the same, (𝒊𝒊) the amplitude stays the same but the frequency increases.

Sound CBSE 9

Represent graphically any two separate diagrams in each case: (𝒊) Two sound waves having the same amplitude but different frequencies. (𝒊𝒊) Two sound waves having the same frequency but different amplitudes. (𝒊𝒊𝒊) Two sound waves having different amplitudes and also different wavelengths.

Sound CBSE 9

What is meant by reflection of sound? (𝒃) Describe an activity to study the reflection of sound. (𝒄) State the laws of reflection of sound.

error: Content is protected !! 💀