Sound Properties, Temperature, and Refraction
In linear acoustics, pitch is primarily associated with frequency, loudness with received intensity, and quality with harmonic waveform; at a stationary boundary frequency remains continuous while wavelength and propagation direction adjust to the new speed.
Why this shows up in the exam
Pitch-quality-loudness matching · Day-night sound refraction · Gas, wind, and temperature comparisons
Learn the idea
Pitch follows frequency, loudness follows intensity, timbre follows waveform, and refraction follows speed gradients. Different perceptual labels track different measurable wave features, while changes of temperature or medium bend rays because local sound speed changes without changing source frequency.
🧠 Memory hook: Source fixes frequency; medium fixes speed and wavelength.
Get this one clearly and it pays off every single time it shows up in the paper. 🎯
Formulas & facts to keep ready
- v proportional to sqrt(T/M) — ideal-gas sound-speed scaling at fixed gamma
- sin(theta1)/v1 = sin(theta2)/v2 — ray refraction relation for two stationary media
- lambda2/lambda1 = v2/v1 — wavelength change at unchanged frequency
How to approach it
- 1Identify the invariant source frequency
- 2Find the local sound speeds
- 3Apply perception or refraction relations without mixing labels
Common slip-ups that cost marks
- •Saying amplitude determines pitch
- •Changing frequency at a stationary interface
- •Using ground velocity instead of velocity relative to the medium
🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.
Original chapter practice
Original questions for this chapter, not past-paper questions or an exact mapping to this individual concept.
A mass of 1 kg is attached to a spring of force constant 100 N/m. Find the angular frequency of small oscillations.
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