Tag: study of sound

Questions Related to study of sound

Which of the following frequency of sound can't be heard by human beings?

audible, infra and ultra sound with its application study of sound physics

  1. 5 Hz

  2. 100 Hz

  3. 500 Hz

  4. 1000 Hz

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Correct Option: A
Explanation:

The generally accepted standard range of audible frequencies is 20 to 20,000 Hz, although the range of frequencies individuals hear is greatly influenced by environmental factors. Frequencies below 20 Hz are  generally felt rather than heard, assuming the amplitude of the vibration is great  enough. So 5 and 10 Hz both can't be heard by human ear in general.

What is frequency of  the sound of vibrations of pendulum which we can't hear?

audible, infra and ultra sound with its application study of sound physics

  1. below 20 Hz

  2. above 20 Hz

  3. 20 Hz

  4. none of these.

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Correct Option: A
Explanation:

The frequency of a vibrating pendulum is quite small and less than 20 Hz which is not in the audible range. Hence, it is not heard.

Which of the following frequency of sound can't be heard by human beings?

audible, infra and ultra sound with its application study of sound physics

  1. 40 Hz

  2. 400 Hz

  3. 4000 Hz

  4. 40,000 Hz

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Correct Option: D
Explanation:

The generally accepted standard range of audible frequencies is 20 to 20,000 Hz, although the range of frequencies individuals hear is greatly influenced by environmental factors. Frequencies below 20 Hz are generally felt rather than heard, assuming the amplitude of the vibration is great enough. So sound with frequency 40,000 Hz can't be heard by human ear in general.

We are able to hear the sounds made by a source, if the frequency of sound is :

audible, infra and ultra sound with its application study of sound physics

  1. Within audible range in air

  2. Within audible range in vacuum

  3. Within audible range in water

  4. Within audible range in $CO _2$

Show answer
Correct Option: A,C,D
Explanation:

sound needs a medium to travel and to hear a sound it should be in audible range in any medium.

so the answer is A, C and D.

Which of the following sound of given frequencies can be heard by us?

audible, infra and ultra sound with its application study of sound physics

  1. $10 Hz$

  2. $20 kHz$

  3. $10 MHz$

  4. $10 GHz$

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Correct Option: B
Explanation:

$20\leq $ Audible frequency $\leq 20 kHz$

Which is not the condition for hearing sound?

audible, infra and ultra sound with its application study of sound physics

  1. There must be a vibrating body capable of transferring energy.

  2. There must be a material medium to pick up and propagate energy

  3. The medium must have a large density.

  4. There must be receiver to receive the energy and interpret it.

Show answer
Correct Option: C
Explanation:

Dense molecules vibrate at slower speeds. The more dense the string is, the slower it will vibrate, and the lower its frequency will be. Instruments often have strings made of different materials. The strings used for low pitches will be made of a more dense material than the strings used for high pitches. 
The more dense the medium the slower the speed of sound. For example steel is 6000 times more denser than air but 2,000,000 times more elastic than air, so sound travels 16 times faster in steel than in air. 

For audible sound, the time interval between two words should be :

audible, infra and ultra sound with its application study of sound physics

  1. $0.1\ s$

  2. $0.2\ s$

  3. $0.4\ s$

  4. $none\ of\ these$

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Correct Option: A
Explanation:

For hearing a distinct sound, the time interval between  original sound and the reflected one must be at least 0.1 s.

Which of the following statement is/are true in case of waves ?

audible, infra and ultra sound with its application study of sound physics

  1. Transverse vibrations are set on the string of a guitar.

  2. As compared to light, a sound wave produced on the moon will take a time about $10^6$ times longer to reach the earth.

  3. A sound note of wavelength 1 cm in air cannot be heard by a man.

  4. Sound travels faster in water than in air.

Show answer
Correct Option: A,C,D
Explanation:

(A) When a guitar string is struck , string is disturbed and the medium (string) particles vibrate perpendicular to the direction of motion disturbance , therefore transverse vibrations are set on the guitar string . -True

(B) Sound wave are longitudinal mechanical waves , which require a medium to travel as there is no medium on moon , so they cannot travel there and can't reach to earth . Whereas light waves ,being electromagnetic waves can travel to earth . -False
(C) If wavelength $\lambda=1cm=0.001m$ and $v=332m/s$ ,
then frequency $f=v/\lambda=332/0.001=332000Hz$ ,
that is an ultrasonic frequency which cannot be heard by a man . -True
(D) Sound travels faster in liquid than gases due to higher elasticity of liquids , therefore sound travels faster in water than in air .  -True

Most students have an audible range of about 50Hz to 50kHz.

audible, infra and ultra sound with its application study of sound physics

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient

Show answer
Correct Option: B
Explanation:

Answer is B.

The generally accepted standard range of audible frequencies is 20 to 20,000 Hz, although the range of frequencies individuals hear is greatly influenced by environmental factors. Frequencies below 20 Hz are generally felt rather than heard, assuming the amplitude of the vibration is great enough. Frequencies above 20,000 Hz can sometimes be sensed by young people. High frequencies are the first to be affected by hearing loss due to age and/or prolonged exposure to very loud noises.
Hence, the statement is false.

Three different vibrating objects produce three types of sounds X, Y and Z.
Sounds X and Y cannot be heard by a man having normal range of hearing but sound Z can be heard easily.
The sound X is used in hospital to break kidney stones of a patient into fine grains which then get flushed out with Urine. The sound similar to that which is produced during an earthquake before the main shock wave is generated.

Name one device in our homes which can produce sound like Z.

audible, infra and ultra sound with its application study of sound physics

  1. oven

  2. doorbell

  3. no such device is there in our homes.

  4. all devices produce such sound

Show answer
Correct Option: B
Explanation:

Ultrasound is used for removing kidney stones.

When ultrasound are targeted on such stone,the stones start vibrating at high frequency. The stone due to this vibratory motion. Breakdown into fine particles. Ultrasounds and infrasounds are not audible to man. Ultrasound have frequency more than 20 kHz. A doorbell can produce an audible sound. 
Infrasound have frequency below 20 Hz
X is ultrasound.
Y is infrasound
Z is audible sound.