one of the following can hear infrasound. This one is :

A. dog B. bat

C. rhinoceros D. humans

‘Note’ os a sound:

A. of a mixture of several frequencies

B. of mixture of only two frequencies

C. of a single frequency

D. always unpleasant to listen to

A key of mechanical piano is first struck gently and then struck again but much harder this time. In the second case:

A. sound will be louder but pitch will not be different

B. sound will be louder and the pitch will also be higher

C. sound will be luder but pitch will be lower

D. both loudness and pitch will remain unaffected

An echo-sounder in a trawler (fishing boat) receives an echo from a shoal of fish 0.4 s after it was sent. If the speed of sound in water is 1500 m/s, how deep is the shoal?

A. 150 m B. 300 m

C. 600 m D. 7500 m

The speed of highly penetrating ultrasonic waves is:

A. lower than those of audible sound waves

B. higher than those of audible sound waves

C. much higher than those of audible sound waves

D. same as those of audible sound waves