← ACARA Digital Technologies Years 7–8

A sample is one volume measurement

One measurement of a sound wave's volume at a single moment in time, stored as one whole number. Many samples taken at equal time steps are dots on the waveform.

Part of: ACARA Digital Technologies Years 7–8 — Representing Text, Images and Sound — Module 49

Understanding A sample is one volume measurement in ACARA Digital Technologies Years 7–8

What it does: The name says when the measurement was taken and the value is a single integer for the volume at that moment. The times are evenly spaced by 0.01 seconds, and one sample is measured at each time. Each sample becomes one integer. The smooth analogue wave is turned into a list of numbers. Samples are taken at regular, equal time steps. This keeps the recording steady and accurate. One sample is one number. So 5 samples gives 5 numbers. A sample measures volume at one instant. It does not measure how long the sound lasts. The variable holds just one integer, which matches the idea that one sample is one number.

Common mistakes: Python lists have no add method. Use append to store each sample (one volume number) in the list: samples.append(volume). A sample is stored as one whole number (an integer), so 7.5 is wrong. It should be a whole number such as sample = 7.

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This module's key terms are also in a printable crossword (Modules 153–172) and word search (Modules 153–188).

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Learning
Duo
What does one sample of a sound wave record?
The whole song from start to finishThe volume of the wave at one moment in time
Matches
sample = 12.5, 80, 33
↓
A sample is only ONE measurement stored as one whole number. This line tries to store three values, one of them a decimal.
Applying
Meanings
Term
sample
Meaning
One measurement of a sound wave's volume at a single moment in time, stored as one whole number. Many samples taken at equal time steps are dots on the waveform.
Practice
sample1 ← 12
Testing
Gaps
sample = (6.7)
Check Answer
Spots
3for volume in wave:
4 samples.add(volume)

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Quick Questions

1. What does one sample of a sound wave record?
A. The volume of the wave at one moment in time ✓
B. The whole song from start to finish
A sample is a single measurement of the wave's volume at one moment. Many samples together describe the whole sound.
2. How is one sample stored in a digital system?
A. As one whole number (an integer) ✓
B. As a smooth, continuous wave
Each sample becomes one integer. The smooth analogue wave is turned into a list of numbers.
3. On a waveform graph, what does each sample look like?
A. A long line covering the whole wave
B. A dot placed on the wave at one point in time ✓
Each sample is one dot on the waveform. Its height shows the volume at that moment.
4. When a computer takes many samples of a sound, when are the measurements taken?
A. At equal time steps, such as every tiny fraction of a second ✓
B. At random times whenever the computer feels like it
Samples are taken at regular, equal time steps. This keeps the recording steady and accurate.
5. If you take 5 samples of a sound wave, how many numbers do you store?
A. 1 number for all 5 samples together
B. 5 numbers, one for each sample ✓
One sample is one number. So 5 samples gives 5 numbers.

Match the Pairs

sample = 142 → One sample is a single measurement of the sound's volume at one moment, stored as one whole number.
samples = [0, 40, 90, 40, 0] → A list of samples taken at equal time steps, each one a dot on the waveform.
A sample is one volume measurement at one moment, stored as a whole number. → volume_at_0_01s = 57
Samples are taken at equal time steps, so each dot on the waveform is the same time apart. → times = [0.00, 0.01, 0.02, 0.03]
sample = 12.5, 80, 33 → A sample is only ONE measurement stored as one whole number. This line tries to store three values, one of them a decimal.
times = [0.00, 0.01, 0.05, 0.06] → The time steps are not equal because the gap jumps from 0.01 to 0.04 between samples. Samples must be taken at equal time steps.

Key Term

sample
One measurement of a sound wave's volume at a single moment in time, stored as one whole number. Many samples taken at equal time steps are dots on the waveform.

Fill in the Blanks

1. sample = round(6.7)
Hint: Type the built-in function that turns a measured volume into a whole number so it can be stored as one integer.
2. samples = [2, 5, 9, 6, 3] print(len(samples))
Hint: Type the built-in function that counts how many samples (numbers) are in the list.
3. for i in range(4): t = i * 0.25 print(t)
Hint: Type the operator that multiplies the step number by the equal time gap, so samples are evenly spaced.
4. samples = [2, 5, 9, 6, 3] print(samples[0])
Hint: Type the index number that picks the first sample, which is one single measurement stored as one number.
5. samples = [2, 5, 9, 6, 3] for s in samples: dot(s)
Hint: Type the loop variable that holds one sample, which is drawn as one dot on the waveform.

Spot the Error

Question 1
A wave = [0, 3, 7, 3, 0]
B samples = []
C for volume in wave:
D samples.add(volume)
Line D — Python lists have no add method. Use append to store each sample (one volume number) in the list: samples.append(volume).
Question 2
A sample = 7.5
B print("Volume:", sample)
C print(type(sample))
Line A — A sample is stored as one whole number (an integer), so 7.5 is wrong. It should be a whole number such as sample = 7.
Question 3
A time = 0
B step = 2
C time = time * step
D print(time)
Line C — Samples are taken at equal time steps, so each step is added to the time. Multiplying leaves time at 0. It should be time = time + step.
Question 4
A samples = [2, 6, 9, 4]
B first = samples[0]
C last = samples[4]
D print(first, last)
Line C — The list holds 4 samples, numbered 0 to 3. Index 4 does not exist and causes an error. The last sample is samples[3].
Question 5
A wave = [0, 4, 8, 4]
B for t in range(len(wave)):
C print(t, wave)
Line C — One sample is one number. Printing wave shows the whole list, not a single sample. It should be print(t, wave[t]).

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