CEA Audio Engineering Principles 2 — Questions and Answers
Question 1: What is the relationship between frequency and wavelength in air at room temperature?
- Wavelength increases as frequency increases
- Wavelength decreases as frequency increases (Correct answer)
- Wavelength and frequency are independent
- Wavelength equals frequency divided by 344
Correct answer: Wavelength decreases as frequency increases
Wavelength (λ) = speed of sound / frequency, so higher frequencies produce shorter wavelengths.
Question 2: Which type of microphone polar pattern rejects sound equally from the sides and rear?
- Omnidirectional
- Cardioid (Correct answer)
- Figure-8 (bidirectional)
- Supercardioid
Correct answer: Cardioid
A cardioid pattern has maximum sensitivity at the front and greatest rejection at the rear (180°).
Question 3: What does THD stand for in audio specifications?
- Total Harmonic Distortion (Correct answer)
- Transient High Definition
- Threshold Headroom Differential
- Tonal Harmonic Deviation
Correct answer: Total Harmonic Distortion
Total Harmonic Distortion measures the ratio of harmonic overtones introduced by a device relative to the fundamental signal.
Question 4: In digital audio, what is the Nyquist theorem's primary requirement?
- Sample rate must equal the highest frequency being recorded
- Sample rate must be at least twice the highest frequency being recorded (Correct answer)
- Bit depth must be at least 16 bits
- Sample rate must be at least 10 times the lowest frequency
Correct answer: Sample rate must be at least twice the highest frequency being recorded
The Nyquist theorem states that to accurately reconstruct a signal, the sample rate must be at least twice the highest frequency present.
Question 5: What phenomenon occurs when two identical audio signals are combined but one is delayed by approximately 180° of phase?
- Comb filtering
- Cancellation (Correct answer)
- Reinforcement
- Haas effect
Correct answer: Cancellation
When two signals are 180° out of phase, their peaks and troughs align inversely, causing destructive interference and cancellation.
Question 6: Which gain structure setting is typically recommended for optimal signal-to-noise ratio in an analog signal chain?
- Keep all faders at unity and adjust input gain to peak near 0 dBFS (Correct answer)
- Set input gain low and boost at output stage
- Keep gain stages as low as possible throughout
- Maximize gain at the first stage and attenuate at each subsequent stage
Correct answer: Keep all faders at unity and adjust input gain to peak near 0 dBFS
Setting input gain so the signal peaks near the top of the operating range and keeping subsequent stages near unity minimizes noise accumulation.
Question 7: What is the primary purpose of dithering in digital audio?
- To increase sample rate
- To add low-level noise that reduces quantization distortion when reducing bit depth (Correct answer)
- To synchronize multiple digital devices
- To compress dynamic range
Correct answer: To add low-level noise that reduces quantization distortion when reducing bit depth
Dithering adds shaped low-level noise to mask quantization errors introduced when reducing bit depth, preserving perceived audio quality.
CEA Audio Engineering Principles 2
What is the relationship between frequency and wavelength in air at room temperature?