Physics 11–12 · Year 11

Pitch and loudness against frequency and amplitude with a sound recorder (syllabus practical)

Module 3: Waves and Thermodynamics (Sound Waves)

Practical, model not builtLow risk

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The idea

Pitch is the ear's response to frequency and loudness to amplitude, and a recorded waveform makes both measurable.

What you need

Signal generator and small loudspeaker, or a phone tone generator
Computer with Audacity (free) and a microphone (the NSW Department of Education Module 3 guide, Activity 6, uses Audacity), or the phyphox audio oscilloscope on a phone
Tuning forks of 256 Hz and 512 Hz, sound level meter or phone sound meter

How to do it

Record a 256 Hz fork and a 512 Hz fork; zoom into the waveform and count the cycles in 10 ms to check the frequency.
Play a 440 Hz tone at three volume settings; record each and read the peak amplitude and the sound level in decibels.
Sweep the generator from 100 Hz to 5 kHz at fixed amplitude and note how pitch rises while the waveform crowds together.
Use the spectrum view to show a single peak for a pure tone and several peaks for a sung note.

What you should see

The 512 Hz recording shows twice as many cycles per 10 ms as the 256 Hz one (5.12 against 2.56 cycles). Louder tones give a taller waveform at the same spacing; a 10 dB rise on the meter corresponds to about 3.2 times the recorded amplitude. A 440 Hz tone has a period of 2.27 ms and a wavelength in air of 0.780 m at 343 m/s.

What changes

What you change: frequency, then amplitude, of the generated tone
What you measure: perceived pitch and loudness; recorded period and amplitude
What you keep the same: microphone distance
room noise
same speaker

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A louder sound travels faster; speed depends on the air, not on loudness.
Higher pitch means bigger waves; it means more cycles per second.

Safety card

Low riskLearners carry it out

Hazards

loud tones damaging hearing

Controls

keep the meter below 85 dB at the ear
no headphones at high volume

Note

Record the activity in RiskAssess (https://www.riskassess.com.au/) and follow the Science ASSIST risk management information sheet (https://asta.edu.au/resource/ais-risk-management-and-risk-assessment/).

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Physics Stage 6 Syllabus (2017), current: Year 11 until the end of 2026, Year 12 until Term 3 2027PH11-10 PH11/12-3 PH11/12-4
Physics 11-12 Syllabus (2025), not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027, first HSC examination 2028PY-11-02 PY-11WS-04
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

All Concept Studio activities