What is the range of frequencies that human ears can detect?

20 Hz to 20,000 Hz

True or False: Sound can travel through vacuum.

False. Sound is a mechanical wave and needs a material medium to propagate.

What do you call sound with frequency above 20,000 Hz?
A) Infrasonic
B) Ultrasonic
C) Supersonic
D) Subsonic

B) Ultrasonic

The formula relating wave velocity, frequency and wavelength is V = _____

Fλ (frequency × wavelength)

What type of wave has compressions and rarefactions?

Longitudinal wave

Why do bats not collide with obstacles while flying in darkness?

They detect obstacles using echoes of their sound waves through sound ranging.

What is the minimum distance required to hear a distinct echo?

17 meters

True or False: Echo reaches sooner on a hot day than cold day.

True. Speed of sound is more on hot day, so echo returns faster.

What does SONAR stand for?
A) Sound Navigation and Recording
B) Sound Navigation and Ranging
C) Sonic Navigation and Ranging
D) Sound Notation and Ranging

B) Sound Navigation and Ranging

Which medical technique uses ultrasonic waves to form heart images?

Echocardiography

Vibrations with constant amplitude in absence of external force are called _____ vibrations.

Free or natural

What happens to amplitude in damped vibrations?

Amplitude decreases continuously due to resistive forces from the surrounding medium.

A tuning fork vibrating in air produces which type of vibrations?
A) Free vibrations
B) Forced vibrations
C) Damped vibrations
D) Resonant vibrations

C) Damped vibrations

When does resonance occur in a vibrating body?

When frequency of external force equals the natural frequency of the body.

True or False: In resonance, the vibrating body oscillates with decreased amplitude.

False. In resonance, the body oscillates with increased or large amplitude.

Why are soldiers asked to break steps while crossing suspension bridges?

To prevent resonance that could cause dangerous vibrations in the bridge structure.

Which characteristic of sound distinguishes a loud sound from a faint one?

Loudness

The loudness of sound is proportional to the _____ of amplitude.

Square

What is 1 decibel defined as?
A) 20% change in intensity
B) 26% change in intensity
C) 30% change in intensity
D) 50% change in intensity

B) 26% change in intensity

Sound levels above _____ dB can cause permanent hearing damage.

120 dB

True or False: Pitch depends on the wavelength or frequency of sound wave.

True. Higher frequency means higher pitch, making sound more shrill.

What distinguishes sounds of same loudness and pitch from different instruments?

Quality or timbre