Cambridge O Level Computer Science · Syllabus 2210 · Data Representation
Sample Rate
What is Sample Rate?
The sample rate is the number of samples taken in a second when an analogue sound wave is converted to binary. A higher sample rate follows the wave more closely, giving a more accurate recording but a larger sound file.
This definition is part of the Data Representation chapter in Cambridge O Level Computer Science.
Sample Rate in context
Sound reaches a microphone as a continuously varying analogue wave. To store it, the wave is sampled: its amplitude is measured at regular intervals, each measurement is recorded as a binary value, and those values are stored in order. Two settings control the process. The sample rate is the number of samples taken in a second. The sample resolution is the number of bits used per sample. Increasing either one makes the stored recording a more accurate representation of the original wave — and increases the file size.
For an uncompressed sound file, the size in bits is the sample rate multiplied by the sample resolution multiplied by the duration in seconds. The logic is simple: the rate tells you how many samples there are each second, the resolution tells you how many bits each sample takes, and the duration tells you how many seconds there are. Multiply the three, then convert down to the unit asked for.
Common mistakes with Sample Rate
- 5. Swapping sample rate and sample resolution. Why it fails They are different quantities with different units. Rate is samples per second; resolution is bits per sample. An "explain" answer that swaps them scores nothing even if the general idea is right. Fix Rate counts how often; resolution counts how precisely.
- M12. "Sample rate and sample resolution mean the same thing." Why it fails They are different quantities measured in different things. Rate counts samples per second; resolution counts bits per sample. Correct model Rate is how often the wave is measured; resolution is how precisely each measurement is recorded. Exam-safe "The sample rate is the number of samples taken in a second; the sample resolution is the number of bits used per sample." Test yourselfHideQ. Which one determines how many different amplitude levels are available?A. The sample resolution: n bits give 2n levels.
- M13. "Increasing the sample rate increases the pitch." Why it fails It confuses the frequency of the recorded sound with the frequency of the sampling. Pitch is a property of the sound; the sample rate is a setting of the recording process. Correct model A higher sample rate takes more measurements of the same wave, giving a more accurate representation and a larger file. The pitch is unchanged. Exam-safe "Increasing the sample rate takes more samples per second, which makes the stored recording more accurate and increases the file size; it does not change the pitch of the sound." Test yourselfHideQ. State two effects of doubling the sample rate.A. The stored recording is a more accurate representation of the original wave, and the file size doubles.
Questions students ask about Sample Rate
What is the difference between sample rate and sample resolution?
Sample rate is the number of samples taken of an analogue sound wave in one second; sample resolution is the number of bits used to store each of those samples. Increasing the sample rate takes more measurements per second, so the recording follows the wave more closely; increasing the sample resolution records each amplitude more precisely. Both changes make the stored recording more accurate but increase the file size — the two settings must never be swapped in an answer.