Lesson 5 - Exam practice
Test your knowledge
Work through these questions as you would in an exam. Answer the MCQ first, then write your answers to the written questions before revealing the mark scheme.
Section 1: Multiple choice
Select one answer per question. Instant feedback appears when you choose.
Question 1 of 5
What does sample rate measure in digital audio?
Sample rate (measured in Hz) is the number of times per second the amplitude of the sound wave is measured and stored as a digital value.
Question 2 of 5
A recording has a sample rate of 44,100 Hz and a bit depth of 16 bits. Which statement is true?
The sample rate means 44,100 measurements are taken each second. Each is stored as a 16-bit binary number. Total bits per second = 44,100 × 16 = 705,600 bits/s per channel.
Question 3 of 5
According to the Nyquist theorem, what must the sample rate be to accurately capture a 10 kHz tone?
The Nyquist theorem states the sample rate must be at least twice the highest frequency. For 10 kHz: minimum sample rate = 2 × 10,000 = 20,000 Hz (20 kHz).
Question 4 of 5
A voice recording uses 8,000 Hz sample rate, 8-bit depth, mono, for 5 seconds. What is the file size in bytes?
Bits = 8,000 × 8 × 5 × 1 = 320,000 bits. Bytes = 320,000 ÷ 8 = 40,000 bytes.
Question 5 of 5
Which change to a recording would double its file size without changing the quality level?
Each of the three changes doubles one factor in the formula (sample rate, channels, or bit depth). All three independently double the file size.
Section 2: Written questions
Write a full answer in your notebook or on paper before checking against the lesson notes.
Written question 1
Calculate the uncompressed file size of a 4-minute stereo recording at 44,100 Hz sample rate and 16-bit depth. Give your answer in megabytes. Show all working.
5 marks
Written question 2
Explain what is meant by quantisation error in digital audio. Describe the effect it has on the quality of a recording and explain how it can be reduced.
4 marks
Written question 3
Evaluate the statement: 'Higher sample rates always produce better audio recordings.' Refer to the Nyquist theorem and practical considerations in your answer.
5 marks