Questions: Digital Audio Fundamentals

Question 1

According to the Nyquist theorem, what sample rate is required to accurately capture a 20 kHz frequency?

• A. 20 kHz
• B. 40 kHz
• C. 96 kHz
• D. 10 kHz

Answer: (B)

The Nyquist theorem requires the sample rate to be at least twice the highest frequency. To capture 20 kHz accurately, you need a minimum of 40 kHz — hence CD audio's 44.1 kHz standard.

Question 2

True or false: Increasing bit depth from 16-bit to 24-bit primarily improves frequency response.

• T. True
• F. False

Answer: False

Bit depth affects dynamic range, not frequency response. More bits mean more amplitude resolution and lower quantization noise — approximately 6 dB more dynamic range per bit.

Question 3

What is dithering in digital audio, and when is it applied?

Model answer: Dithering is the addition of low-level random noise to a signal before reducing bit depth. It distributes quantization error more evenly, converting harsh distortion into benign, spectrally shaped noise.

Without dithering, truncating a 24-bit file to 16-bit introduces correlated quantization distortion that sounds gritty. Dithering masks this by trading distortion for gentler noise.

Question 4

A producer is recording a full orchestra with wide dynamic variation. Which recording format is most appropriate?

• A. 8-bit / 22.05 kHz — smaller files reduce storage burden
• B. 16-bit / 44.1 kHz — CD quality is sufficient
• C. 24-bit / 96 kHz — greater headroom preserves quiet details and loud peaks
• D. 32-bit float / 8 kHz — float handles clipping

Answer: (C)

24-bit gives ~144 dB dynamic range, capturing both the quietest violin harmonics and loudest brass crescendos without quantization noise. 96 kHz allows filtering headroom for clean reconstruction.