← IGCSE Computer Science Paper 1

Effect of sample rate and resolution on accuracy and file size

Raising the sample rate or sample resolution records the sound more accurately, but it also makes the audio file bigger. Lowering either does the opposite: less accurate, smaller file.

Part of: IGCSE Computer Science 0478 — 1.2 Text, Sound and Images — Module 15, IGCSE Computer Science 0478 — 1.3 Data Storage and Compression — Module 36, ACARA Digital Technologies Years 9–10 — Data Compression — Module 30

Understanding Effect of sample rate and resolution on accuracy and file size in IGCSE Computer Science Paper 1

What it does: Recording B takes more samples each second, so it follows the wave more closely and stores more data. Fewer bits per sample means fewer volume levels and less data to store, so quality and file size both fall. With few samples, quick changes in the wave happen between samples and are lost.

Common mistakes: 44100 is greater than 8000, so recording 1 has the higher sample rate and the bigger file. The condition should be rate1 > rate2. A low sample rate takes few samples, so it misses detail of the sound wave. The line should say it misses wave detail.

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This module's key terms are also in a printable crossword (Modules 43–58) and word search (Modules 28–58).

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Learning

Duo

A student raises the sample rate of a recording. What happens to the file size?

It gets larger because more samples are storedIt gets smaller because the sound is cleaner

Matches

sample_rate: 44100 -> 8000 # file gets bigger

↓

Lowering the sample rate means fewer samples are stored, so the file gets smaller, not bigger. Accuracy also drops.

Applying

Meanings

Term

higher sample rate or resolution

Meaning

Raising the sample rate or sample resolution records the sound more accurately, but it also makes the audio file bigger. Lowering either does the opposite: less accurate, smaller file.

Practice

IF rate_B > rate_A THEN

Testing

Gaps

IF newRate oldRate THEN

Check Answer

Spots

2rate2 ← 8000

3IF rate1 < rate2 THEN

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Quick Questions

1. A student raises the sample rate of a recording. What happens to the file size?

A. It gets larger because more samples are stored ✓

B. It gets smaller because the sound is cleaner

More samples per second means more data to store, so the file gets bigger.

2. Which recording is MORE accurate to the original sound wave?

A. A recording with a high sample rate ✓

B. A recording with a low sample rate

Taking more samples each second captures more detail of the wave, so it is a closer copy of the original.

3. A sound is recorded with a very low sample rate. What is the likely problem?

A. The volume levels become too fine to store

B. Detail of the wave is missed between samples ✓

With few samples, quick changes in the wave happen between samples and are lost.

4. A sound is recorded with a low sample resolution (few bits per sample). What does the volume sound like?

A. Coarse, with only a few volume levels to choose from ✓

B. Smooth, with many different volume levels

Fewer bits per sample means fewer possible volume levels, so each sample is rounded to a rougher value.

5. Two recordings of the same song are made. Recording A uses 16 bits per sample and recording B uses 8 bits per sample. Both use the same sample rate. Which file is larger?

A. Recording B, because it has less accurate samples

B. Recording A, because each sample uses more bits ✓

Each sample in A takes more bits, so A is bigger. It is also more accurate because it has more volume levels.

Match the Pairs

sample_rate = 8000 → A low sample rate takes few samples per second, so it misses detail of the wave. The recording is less accurate but the file is small.

sample_resolution = 4 → A low sample resolution gives only a few volume levels, so the sound is coarse and less accurate. The file is smaller.

Two recordings of the same sound: the one with the higher sample rate is more accurate but has the larger file → A: rate = 8000, B: rate = 44100 -> B is more accurate, size(B) > size(A)

Lowering the sample resolution gives coarser volume levels and makes the file smaller → resolution: 16 -> 4, accuracy goes down, file size goes down

sample_rate: 44100 -> 8000 # file gets bigger → Lowering the sample rate means fewer samples are stored, so the file gets smaller, not bigger. Accuracy also drops.

resolution: 16 -> 24 # same file size → Raising the sample resolution means more bits for every sample, so the recording is more accurate and the file gets larger, not the same size.

Key Term

higher sample rate or resolution

Raising the sample rate or sample resolution records the sound more accurately, but it also makes the audio file bigger. Lowering either does the opposite: less accurate, smaller file.

Fill in the Blanks

1. IF newRate > oldRate THEN accuracy ← "higher" fileSize ← "larger"

Hint: Type the comparison operator that means the new sample rate is higher than the old one.

2. resolution ← 4 IF resolution < 8 THEN volumeLevels ← "coarse"

Hint: Type the variable name for the setting that decides how many volume levels each sample can use.

3. rate ← 44100 IF rate > 8000 THEN OUTPUT "Bigger file, better accuracy"

Hint: Type the keyword that displays a message to the user.

4. rate ← 1000 IF rate < 8000 THEN OUTPUT "Misses detail of the wave"

Hint: Type the keyword that follows the condition on an IF line.

5. resolution ← 8 resolution ← resolution + 8 OUTPUT "More levels, larger file"

Hint: Type the assignment symbol that stores the increased resolution back in the variable.

Spot the Error

Question 1

A rate1 ← 44100

B rate2 ← 8000

C IF rate1 < rate2 THEN

D OUTPUT "File 1 is bigger"

Line C — 44100 is greater than 8000, so recording 1 has the higher sample rate and the bigger file. The condition should be rate1 > rate2.

Question 2

A sampleRate ← 8000

B OUTPUT "Captures all detail"

C OUTPUT "Small file"

Line B — A low sample rate takes few samples, so it misses detail of the sound wave. The line should say it misses wave detail.

Question 3

A resolution ← 24

B OUTPUT "Coarse volume levels"

C OUTPUT "Small file"

Line A — The output describes low resolution (coarse levels, small file). A high value like 24 bits would give fine levels and a larger file, so the value should be low, such as 4.

Question 4

A resA ← 16

B resB ← 8

C IF resA > resB THEN

D OUTPUT "A is smaller file"

Line D — Recording A has the higher sample resolution, so it is more accurate and its file is larger, not smaller.

Question 5

A sampleRate ← 22050

B sampleRate ← sampleRate / 2

C OUTPUT "Better, bigger file"

Line B — The output says the recording gets better and the file bigger, which needs a higher rate. The rate should be multiplied (increased), not divided.

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