What is the lowest limit of audible frequency?

A whistle of frequency 540 Hz rotates in a circle of radius 2 m at an angular speed of 15rads^(-1) . What is the lowest and highest frequency heard by a listener a long distance away at rest with respect to centre of the circle ? Can the apparent frequecny be ever equal to the actual frequency? Take V=330ms^(-1) .

A traffic policeman sounds a whistle to stop a car-driver approaching towards him. The car-driver does not stop and takes the plea in court that because of the Doppler shift, the frequency of the whistle reaching him might have gone beyond the audible limit of 20 kHz and he did not hear it. Experiments showed that the whistle emits a sound with frequency close to 16 kHz. Assuming that the claim of the driver is true, how fast was he driving the car ? Take the speed of sound in air to be 330 m s^-1 . Is this speed practical with today's technology ?

What is the audible range of frequency?

What is the frequency range of audible sound?

What is the tolerable limit of fluoride ions in drinking water ? What happens if its exceeds 10 ppm ?

What is the limitation of Hooke's law?