Sound Design Waves And Sound 5

Question 1

What is the speed of sound in dry air at approximately 20°C (68°F)?

Accepted Answer

1,125 ft/s (343 m/s)

Answer

Sound travels at approximately 343 m/s (about 1,125 ft/s) in dry air at 20°C, which is a key reference for delay and timing calculations.

Question 2

Which type of boundary condition exists at the closed end of an acoustic pipe?

Accepted Answer

Node (displacement node / pressure antinode)

Answer

At a closed end, air cannot move freely, creating a displacement node and a pressure antinode — maximum pressure variation occurs there.

Question 3

Refraction of sound waves occurs when they pass between two media of different:

Accepted Answer

Wave speeds

Answer

Sound refracts (changes direction) when it crosses a boundary where wave speed differs, such as between air layers of different temperatures.

Question 4

A sound wave's amplitude directly determines which perceptual attribute?

Accepted Answer

Loudness

Answer

Amplitude corresponds to the physical magnitude of pressure variation, which we perceive as loudness.

Question 5

In a room, the 'critical distance' refers to the point where:

Accepted Answer

Direct sound and reverberant field have equal intensity

Answer

The critical distance is where the direct sound level equals the reverberant sound level; beyond it, the room sound dominates over the direct source.

Sound Design Practice Test