Wavelength

The physical length of one complete sound wave cycle, inversely proportional to frequency.

Wavelength (λ, lambda) is the physical distance a sound wave travels during one complete cycle. It's inversely proportional to frequency: low frequencies have long wavelengths, high frequencies have short wavelengths.

At typical room temperatures (20°C), the speed of sound is approximately 343 m/s. This gives us: • 20 Hz: λ = 17.2 meters • 100 Hz: λ = 3.4 meters • 1,000 Hz: λ = 34.3 centimeters • 10,000 Hz: λ = 3.4 centimeters

Wavelength is crucial in acoustics because: • Room modes occur when wavelengths fit between room dimensions • Absorber thickness relative to wavelength determines effectiveness • Diffuser well depths are calculated from design wavelength • Objects smaller than the wavelength don't effectively scatter sound

Understanding wavelength helps explain why bass is difficult to control (long wavelengths need thick treatment) and why small diffusers only work at high frequencies.

Formula

λ = c / f

λ = Wavelength (meters)
c = Speed of Sound (~343 m/s)
f = Frequency (Hz)

Practical Example

Designing a diffuser for 500 Hz

λ = 343 / 500 = 0.686 m (68.6 cm)

Maximum well depth will be about λ/2 = 34 cm. The diffuser will scatter effectively from roughly 250 Hz to 2000 Hz.

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