CEA Studio Acoustics and Room Treatment 2

Question 1

What is the 'critical distance' in room acoustics?

Accepted Answer

The distance from a sound source at which the direct sound level equals the reverberant field level

Answer

Critical distance is the point in a room where the level of the direct sound field equals the level of the reverberant (diffuse) field. Recording microphones placed within the critical distance capture more direct sound; beyond it, more room ambience is captured.

Question 2

Which formula is used to calculate the three primary axial room modes?

Accepted Answer

f = c / (2L), where c is the speed of sound and L is the room dimension

Answer

Axial room modes occur at frequencies where the room dimension equals half wavelengths of the sound. The formula f = c / (2L) — where c ≈ 344 m/s is the speed of sound and L is the room length, width, or height — gives the fundamental mode for each dimension.

Question 3

What is the purpose of a 'floating floor' in studio construction?

Accepted Answer

To mechanically decouple the studio floor from the building structure, reducing structure-borne vibration transmission

Answer

A floating floor is a floor structure that rests on resilient isolators (neoprene pads, springs) so it is mechanically decoupled from the building slab. This reduces the transmission of impact noise and low-frequency vibration between floors, critical for professional studio isolation.

Question 4

What acoustic problem does 'comb filtering' cause in a studio monitoring environment?

Accepted Answer

Frequency response irregularities with alternating peaks and nulls caused by path-length differences between direct and reflected sound

Answer

Comb filtering creates a series of evenly spaced peaks and notches in the frequency response when a direct signal and a delayed reflection combine. It is caused by the time-offset between direct sound from the speaker and a reflection from a nearby surface.

Question 5

What is the 'Sabine formula' used to calculate in room acoustics?

Accepted Answer

The reverberation time (RT60) based on room volume and total sound absorption

Answer

The Sabine formula, RT60 = 0.161 × V / A, estimates reverberation time where V is the room volume (m³) and A is the total absorption (m² Sabins). It is a fundamental tool for predicting how much acoustic treatment is needed in a space.

(CEA) Certified Audio Engineer Practice Test

(CEA) Certified Audio Engineer Practice Test

CEA Studio Acoustics and Room Treatment 2