WAV-29

Sound pressure level

SPL re 20 µPa.

Reading speed

GoverningSound pressure level

Governing equation

L_p=20\log_{10}(p/p_0)

where

p: p (Pa)
Lp: Sound pressure level (dB)

Lecture brief

Historical brief

d’Alembert’s wave equation, Snell, the thin-lens maker, Doppler and Bragg interference are the classical optics-and-sound toolkit. The lab is propagation, image and shift. This sheet (WAV-29 — Sound pressure level) is the form associated with Sound pressure level. Working symbols: $p$ $\rightarrow$ $Lp$ . SPL re 20 µPa. Pedagogical SI sheet with a live model and a swept parameter.

Purpose

Purpose: compute

Lp

from

p

in Waves & optics via

L_p=20\log_{10}(p/p_0)

SPL re 20 µPa. Use it when a real waves & optics question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

p = 0.200\,\mathrm{Pa}

, the governing relation

L_p=20\log_{10}(p/p_0)

yields

Lp = 80.000\,\mathrm{dB}

. One governing identity, SI units, a single sweep on the sheet. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

p p0.2 Pa

Outputs

Sound pressure level Lp80.000 dB

Reading speed

Watch on YouTube

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Narration of this film

One governing identity, SI units, a single sweep on the sheet.

SPL re 20 µPa. Pedagogical SI sheet with a live model and a swept parameter.

Reading speed

Watch on YouTube