Sound — Set 5
Physics · ध्वनि · Questions 41–50 of 60
The usual audible frequency range for a healthy human ear is approximately?
Correct Answer: D. 20 Hz to 20 kHz
Humans generally hear frequencies from about 20 Hz up to about 20 kHz. Below this range the sound is called infrasonic and above it ultrasonic. Hearing range often narrows with age and loud noise exposure.
Ultrasound refers to sound waves with frequency?
Correct Answer: A. Greater than 20 kHz
Ultrasound means frequencies higher than the upper limit of human hearing. The common cutoff is above about 20 kHz. Ultrasound is widely used in medical imaging and industrial testing.
Infrasound refers to sound waves with frequency?
Correct Answer: D. Less than 20 Hz
The correct answer is 'Less than 20 Hz'. Infrasound means frequencies below the lower limit of human hearing. The common cutoff is below about 20 Hz. Some natural events like earthquakes can produce infrasound.
The speed of sound in dry air at about 20°C is closest to?
Correct Answer: D. 343 m/s
At room temperature, the speed of sound in air is about 343 meters per second. This value changes with temperature and a bit with humidity. It is much smaller than the speed of light.
The speed of sound in water is approximately?
Correct Answer: D. 1500 m/s
Sound travels faster in water than in air because water is much less compressible. A typical value is around 1500 meters per second. This is why sonar works effectively in oceans.
A commonly quoted speed of sound in steel is about?
Correct Answer: C. 50 m/s
Sound can travel very fast in stiff solids like steel. A typical value is around 5000 meters per second. The high stiffness of steel helps vibrations propagate quickly.
SONAR stands for?
Correct Answer: D. Sound Navigation and Ranging
SONAR is an acronym for Sound Navigation and Ranging. It uses sound pulses and their echoes to detect objects and measure distance. It is widely used in submarines and depth measurement.
The correct wave relation connecting speed (v), frequency (f), and wavelength (λ) is?
Correct Answer: B. v = fλ
Wave speed equals frequency multiplied by wavelength. This relation holds for sound waves in a given medium. If frequency stays constant and speed changes, wavelength changes accordingly.
A distinct echo is generally heard when the time gap between direct sound and reflected sound is at least?
Correct Answer: D. 0.1 s
The ear separates two sounds as different if the delay is about 0.1 seconds or more. Shorter delays blend into reverberation rather than a clear echo. In air this corresponds to a reflector roughly 17 meters away or more.
Sound intensity level in decibels is commonly defined as?
Correct Answer: C. L = 10 log10(I/I0)
The correct answer is 'L = 10 log10(I/I0)'. Intensity level compares intensity to a reference using a logarithm. The standard formula is L equals 10 times log base 10 of I divided by I0. This makes very large intensity ranges easier to express.