Digital Audio Basics

Question 1

When audio is recorded, _________ energy is converted to _________ energy.

Answer 1

SONIC energy is converted to ELECTRICAL energy

Question 2

What is a SAMPLE (when referring to the basics of digital audio)?

Answer 2

A SAMPLE is an instantaneous measurement of the AMPLITUDE of an audio signal.

Question 3

What is a SAMPLE RATE?

Answer 3

The number of samples (instantaneous measurements of amplitude) per second.

Question 4

How do we measure the SAMPLE RATE?

Answer 4

In Hertz and Kilohertz, just like frequency

Question 5

What is the Nyquist-Shannon sampling theorem?

Answer 5

In order to accurately record or reproduce a sound, the sample rate must be at least twice the highest frequency of that sound. In other words, you need at least one sample from each compression phase, and each rarefaction phase, of a waveform.

Question 6

What happens if less than two samples per cycle are recorded?

Answer 6

FOLDBACK or ALIASING: a lower frequency is created

Question 7

What is the Nyquist frequency?

Answer 7

The frequency that is 1/2 of the sample rate, or the highest frequency that can be accurately recorded.

Question 8

Is there distortion in digital audio near the Nyquist frequency?

Answer 8

Yes

Question 9

What is the Nyquist frequency at a 44.1k sample rate?

Answer 9

22.05, which is almost in the range of human hearing, meaning that at a 44.1k sample rate, you might hear it (especially with sounds with a lot of high frequency content, like cymbals.

Question 10

What is bit depth?

Answer 10

The number of 1’s and 0’s included in one sample.

Question 11

What are the most common bit depths in the audio production world?

Answer 11

16-bit and 24-bit

Question 12

What are the 2 benefits of higher bit depths?

Answer 12

ACCURACY (the more bits in a sample, the more accurately you can measure amplitude)

and

GREATER DYNAMIC RANGE (each bit gives you approximately 6 db of dynamic range)

Question 13

How much dynamic range is represented by 1 bit?

Answer 13

Approximately 6 db

Question 14

What is the maximum dynamic range of 24 bit audio?

Answer 14

144 db