Hertz and kilohertz
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. Sample rate is measured in which unit?
2. How many hertz are in 1 kHz?
3. What is 44.1 kHz written in hertz?
4. A sound is sampled at 8 kHz. How many samples are taken each second?
5. Why does kHz use 1000 instead of 1024?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 11 kHz = 1000 Hz | AThe value was not multiplied by 1000 correctly. 44.1 x 1000 = 44100, so it should be 44.1 kHz = 44100 Hz. | |
| 244.1 kHz = 44100 Hz | BA CD-quality sample rate of 44100 samples taken every second. | |
| 3Sample rate is measured in hertz, which means samples per second | COne kilohertz is 1000 samples per second, because frequency units use 1000. | |
| 4Convert kHz to Hz before calculating by multiplying by 1000 | Dsample_rate = 8000 Hz | |
| 51 kHz = 1024 Hz | EHz = kHz * 1000 | |
| 644.1 kHz = 441 Hz | FKilohertz uses 1000, not 1024. 1024 is for storage units such as KiB. It should be 1 kHz = 1000 Hz. |
C
Definitions
1 kHz = 1000 Hz
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
Sample rate is measured in __
2.
44.1 kHz = _____ Hz
3.
khz <- 22.05
hz <- khz * ____
4.
1 ___ = 1000 Hz
5.
1 Hz = 1 ______ per second
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
rate_khz ← 44.1
B
rate_hz ← rate_khz * 1000
C
seconds ← 10
D
samples ← rate_hz + seconds
E
OUTPUT samples
Question 2
A
rate_khz ← 8
B
rate_hz ← rate_khz * 1024
C
OUTPUT rate_hz
Question 3
A
// 1 kHz is 1000 Hz
B
rate_khz ← 22.05
C
rate_hz ← rate_khz / 1000
D
OUTPUT rate_hz
Question 4
A
rate_hz ← 22050
B
rate_khz ← rate_hz * 1000
C
OUTPUT rate_khz
Question 5
A
rate_khz ← 16
B
rate_hz ← rate_khz * 1000
C
OUTPUT "Sample rate:"
D
OUTPUT rate_hz, "kHz"
Answer Key
Hertz and kilohertz
Section A: Quick Questions
Q1
A — Hertz (Hz), samples per second
Q2
B — 1000 Hz
Q3
A — 44100 Hz
Q4
B — 8000
Q5
A — It is a frequency unit, not a storage unit
Section B: Match the Pairs
Q1
1 kHz = 1000 Hz → One kilohertz is 1000 samples per second, because frequency units use 1000.
Q2
44.1 kHz = 44100 Hz → A CD-quality sample rate of 44100 samples taken every second.
Q3
Sample rate is measured in hertz, which means samples per second → sample_rate = 8000 Hz
Q4
Convert kHz to Hz before calculating by multiplying by 1000 → Hz = kHz * 1000
Q5
1 kHz = 1024 Hz → Kilohertz uses 1000, not 1024. 1024 is for storage units such as KiB. It should be 1 kHz = 1000 Hz.
Q6
44.1 kHz = 441 Hz → The value was not multiplied by 1000 correctly. 44.1 x 1000 = 44100, so it should be 44.1 kHz = 44100 Hz.
Section C: Definitions
Q1
1 kHz = 1000 Hz — Sample rate is measured in hertz (Hz), the number of samples per second. 1 kHz is 1000 Hz, so 44.1 kHz is 44100 Hz. Frequency uses 1000, not 1024.Section D: Fill in the Blanks
Q1
Sample rate is measured in HzQ2
44.1 kHz = 44100 HzQ3
khz <- 22.05
hz <- khz * 1000Q4
1 kHz = 1000 HzQ5
1 Hz = 1 sample per secondSection E: Spot the Error
Q1
D — The rate is in samples per second, so the total number of samples is rate_hz multiplied by seconds, not added. It should be samples ← rate_hz * seconds.
Q2
B — kHz is a frequency unit, so 1 kHz is exactly 1000 Hz. 1024 is only used for storage units. It should be rate_hz ← rate_khz * 1000.
Q3
C — Going from kHz to Hz means multiplying by 1000, because Hz is the smaller unit. Dividing would give a number that is far too small. It should be rate_hz ← rate_khz * 1000.
Q4
B — Going from Hz to kHz means dividing by 1000, because kHz is the larger unit. Multiplying would give a huge wrong value. It should be rate_khz ← rate_hz / 1000.
Q5
D — rate_hz holds a value in hertz (16000), so the label must be "Hz". Labelling 16000 as kHz would mean 16 million Hz. It should be OUTPUT rate_hz, "Hz".