Use the approximate human audible frequency range
Recall 20 Hz to 20 000 Hz as an approximate range and distinguish frequency boundaries from guaranteed hearing.
Section P3.3 · Sound
Cross-referenced from the related Cambridge IGCSE Chemistry 0620 or Physics 0625 teaching to the 0652 syllabus. Exact 0652 Core/Supplement objective coverage and this final-series course’s examiner fit still need specialist review. Written practice is self-checked and does not predict a Cambridge grade or demonstrate supervised laboratory competence.
Before you begin
- Define frequency in hertz.
- Convert the kilo prefix.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What does 2.0 kHz mean?
What you will learn
- State the approximate audible frequency range.
- Convert kilohertz and interpret the limits without assuming identical listeners.
Remember the two frequency limits
The approximate range audible to humans is 20 Hz to 20 000 Hz, often written 20 Hz to 20 kHz. These are frequencies, not wave speeds or loudness values. A 2.0 kHz sound has frequency 2000 Hz and lies within this approximate range.
Below the lower reference is infrasonic frequency; above the upper reference is ultrasonic frequency. The boundaries describe an approximate human range, not an exact ability shared by every person. Age, individual hearing and signal level affect actual audibility.
Keep pitch and hearing evidence separate
Frequency relates to pitch within the audible range. Increasing amplitude can make an otherwise audible sound louder, but it does not convert a 30 kHz signal into a lower-frequency signal. Frequency and amplitude must be varied separately when interpreting observations.
Being within the approximate range does not guarantee a particular observer hears a weak signal. Conversely, a detector can measure frequencies outside ordinary human hearing. Use frequency data to classify the signal and direct evidence to describe the listener's response.
Sources for this lesson
Pause and explain
Which stated frequency is above the approximate upper audible limit?
Worked example
Classify 2.0 kHz and 30 kHz against the approximate human audible range.
Show the worked solution
- 2.0 kHz = 2000 Hz, inside 20–20 000 Hz.
- 30 kHz = 30 000 Hz, above the upper reference.
- Actual hearing of the first still depends on the listener and signal strength.
Answer 2.0 kHz is within the approximate range; 30 kHz is above it.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
State the approximate human audible frequency range in hertz.
Give me a hint
Give both low and high references.
Compare my reasoning
- The lower reference is 20 Hz.
- The upper is 20 000 Hz.
- This is an approximate range.
Approximately 20 Hz to 20 000 Hz.
Look for these in your work
- Include both limits.
- Use frequency units.
Place 10 Hz, 500 Hz and 25 kHz relative to that range.
Give me a hint
Convert the kilohertz value before comparing.
Compare my reasoning
- 10 Hz is below 20 Hz.
- 500 Hz lies within the range.
- 25 kHz = 25 000 Hz is above it.
Below; within; above, respectively.
Look for these in your work
- Convert the prefix.
- Preserve the approximate range condition.
A weak 1000 Hz signal is not heard by one observer. Does this disprove the approximate range?
Give me a hint
Separate frequency eligibility from level and individual response.
Compare my reasoning
- 1000 Hz lies inside the approximate range.
- Audibility also depends on level and the listener.
- A negative response does not establish a new universal boundary.
No; the range does not guarantee hearing every weak signal by every listener.
Look for these in your work
- Use the frequency data.
- State the other audibility factors.
Common mistakes
- 20 kHz equals 20 000 Hz.
- The range is approximate, not a universal hearing guarantee.
- Amplitude does not change frequency classification.
What can you explain now?
What is the approximate upper audible frequency reference?
Compare with the explanation
20 000 Hz, or 20 kHz.
It is a frequency limit rather than a propagation speed or loudness.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Recall and apply the approximate range, convert kHz and explain why classification is not guaranteed perception.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.