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Q1. The audible range of sound in humans is

• 1) 10 Hz - 10,000 Hz
• 2) 20 Hz - 15,000 Hz
• 3) 20 Hz - 20,000 Hz
• 4) 15 Hz - 15,000 Hz

Solution

The audible range of sound in humans is 20 Hz - 20,000 Hz.

Q2. Sound travels due to vibrations of a body in a medium.

• 1) No
• 2) Depends on the body
• 3) Sound has no relation with vibrations
• 4) Yes

Solution

Sound indeed travels due to vibrations of a body in a medium.

Q3. What change would you expect in the characteristic of a musical sound if its frequency is increased?

• 1) Amplitude will increase
• 2) Wavelength will increase
• 3) Pitch will increase
• 4) Loudness will increase

Solution

The frequency of a sound determines the pitch of a sound. Higher the frequency of vibration, higher is the pitch.

Q4. Sound quality is also termed as

• 1) Pitch
• 2) Timbre
• 3) Oscillation
• 4) Frequency

Solution

Timbre or quality of sound is a characteristic by virtue of which we can distinguish between two sounds of same pitch and loudness.

Q5. Noise pollution can cause

• 1) Goitre
• 2) Diabetes
• 3) High Blood Pressure
• 4) Scurvy

Solution

Noise leads to irritability which increases the blood pressure. The other ailments are related to deficiencies or physiological factors.

Q6. Repetition of sound, when reflected from a distant body is

• 1) Oscillation
• 2) Reverberation
• 3) Refraction
• 4) Echo

Solution

Echo is a phenomenon by which sound travels and returns back after reflection from a distant body.

Q7. Define shrill and sound quality.

Solution

Shrill: The sound produced by a vibrating object with a high frequency is called shrill. Sound quality: The quality of a musical sound is that characteristics by virtue of which we can distinguish between two sounds of the same pitch and loudness produced by two different musical instruments or by different voices.

Q8. __________ is made of three bones—malleus, anvil and stirrup. 

• 1) Cochlea
• 2) Tympanic membrane
• 3) Auditory nerve
• 4) Ossicle

Solution

The ossicle is made of three bones—malleus, anvil and stirrup 

Q9.  Define:(a) Amplitude(b) Time period(c) Frequency

Solution

(a) Amplitude: The maximum displacement from the mean position during an oscillation is called the amplitude of the oscillation. (b) Time period: The time taken to complete one oscillation is called the time period of the oscillation. (c) Frequency: The number of oscillations per second is called the frequency of oscillation.

Q10. Which of the following will remain unchanged when a sound wave travels in air or in water?

• 1) Frequency
• 2) Amplitude
• 3) Speed
• 4) Wavelength

Solution

Frequency will remain unchanged when a sound wave travels in air or in water.    

Q11. Noise pollution is controlled by

• 1) Carburetor
• 2) Alternator
• 3) Silencer
• 4) Regulator

Solution

A silencer dampens the noise produced by the engine and hence controls noise pollution.

Q12. Sound is created by

• 1) Vibration of the air particles surrounding the source
• 2) Vibration of ear drums
• 3) Longitudinal waves
• 4) Sound waves

Solution

Sound is a form of energy which is created by a vibrating object when it vibrates the air particles around it.

Q13. Define:Noise

Solution

 Noise: Unwanted, discomfort causing sound from any source is called noise.

Q14. What are the three main causes of oceanic sound pollution?

Solution

Oceanic sound pollution is caused by (i) under water blasting, (ii) dredging and (iii) under water earthquakes.

Q15. Quality of sound is determined by

• 1) Amplitude and loudness
• 2) Frequency and amplitude
• 3) Amplitude and pitch
• 4) Frequency and pitch

Solution

Quality of sound is determined by frequency and amplitude.

Q16. Noise pollution is caused above a sound level of

• 1) 50 decibels
• 2) 20 decibels
• 3) 10 decibels
• 4) 90 decibels

Solution

Human ears can tolerate sounds up to a level of 80 decibels. Beyond this it causes irritation and hence the levels above 90 decibels are considered as noise pollution.

Q17. (i) What determines the shrillness of the sound produced by a body?(ii) What are the three main causes of oceanic sound pollution?

Solution

(i) Shrillness of the sound produced by a body is determined by the frequency of the vibrating body.(ii) Oceanic sound pollution is caused by (a) under water blasting, (b) dredging and (c) under water earthquakes.

Q18. Differentiate between Intensity and Loudness.

Solution

Intensity of sound at a point is defined as the amount of sound energy flowing per second normally through unit area around that point. Loudness is a measure of amount of sensation produced in the ears of the listener. Intensity does not depend on the listener whereas the loudness depends on the listener.

Q19. Do you know why bees buzz? Is it the way they communicate?

Solution

No, bees do not communicate by buzzing. Buzzing sound of bees is produced by their mouths. The buzzing comes from the wings of the bee, which it flaps even while feeding on the nectar of a flower.

Q20. The type of sound used for scanning and imaging the position and growth of a human foetus is

• 1) Audible sound
• 2) Infrasonic sound
• 3) Ultrasonic sound
• 4) Infra-red radiation

Solution

Ultrasonic sounds are reflected back by objects in their path. The echoes thus formed are used to get the details about the object.

Q21. How is sound produced in humans?

Solution

Larynx is the organ that is involved in the production of sound in humans. It is also called as voice box. The voice box is situated in the neck at the upper end of the wind pipe. The sound produced is controlled by vocal cords which are thin membranes stretched across the voice box. There are muscles that are attached to the vocal cords. These muscles can vary the tension in the vocal cords. With the help of these muscles we can make different sounds.

Q22. List the factors on which the speed of propagation of sound depends on?

Solution

Speed of propagation of sound depends on(i) Temperature(ii) Nature of the media(iii) Humidity

Q23. How do we recognize the different sounds of same loudness? Give example from everyday life.

Solution

Different sounds of same loudness can be recognized by recognizing the frequencies. This is how we identify a voice of a child, women and man, even when they speak with same loudness.

Q24. Why do sound travel faster in solids?

Solution

Sound travels fastest in solids because molecules in a solid do not move very far from their mean position and bounce back very quickly. Whereas liquids and gases are poor transmitters.

Q25. How do we hear sound? Explain

Solution

(i) Sound travels through our outer ear into a canal which ends with a stretched membrane called eardrum. (ii) Sound vibrations make the eardrum vibrate. (iii) The eardrum sends vibrations to the inner ear. From there the signal goes to the brin and that is how we hear.

Q26. Name the unit for the measurement of loudness of sound.

Solution

Loudness of sound is measured in decibels (dB). A sound of about 50 to 80 decibels is considered as audible sound.

Q27. Name some common ailments suffered by people living in a residential area close to the airport.

Solution

Common ailments suffered by people living in a residential area close to the airport are (i) Irritability, (ii) Cardio vascular disease, (iii) Hypertension, (iv) Lack of sleep (v) Hearing impairment.

Q28. Why is a woman's voice different from a man's voice?

Solution

In human beings, vocal cords are responsible for the difference of woman's voice from man's voice. When the cords are tight and thin, the sound is of higher pitch or frequency. On the other hand, when the cords are loose and thick the sound is of low pitch or frequency. Men have longer vocal cords than women. That is why the frequency of a sound produced by women is of a higher frequency than the sound produced by men.

Q29. Can sound travel in vacuum? Explain

Solution

Sound cannot travel in vacuum because sound travels by producing a vibration in the molecules of the medium surrounding it and there are no molecules in vacuum.

Q30. Define pitch and timbre.

Solution

1. Pitch is the effect or sensation produced in the brain due to the sound of some particular frequency. Pitch depends upon the frequency of a vibrating body. It means that higher the pitch more is the frequency and lower the pitch less is the frequency. 2. Timbre or sound quality is that characteristics by virtue of which we can distinguish between two sounds of the same pitch and loudness produced by two different musical instruments or two different voices.

Q31. Differentiate between high-pitch sound and low-pitch sound.

Solution

High-pitch sound: The sound produced by an object vibrating with a high frequency is called shrill or high-pitched sound. Low-pitch sound: The sound produced by an object vibrating with a low frequency is described as flat or low-pitched sound.