Room boundaries alter a sound source’s radiated power, not just its perceived sound
Evidence
Waterhouse (1955) extended work by Rayleigh (1964) and confirmed experimentally that the power output of a source is affected by the presence of boundaries, for example the walls in a room. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2134
Waterhouse (1955) extended work by Rayleigh (1964) and confirmed experimentally that the power output of a source is affected the presence of boundaries, for example the walls in a room. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2182
Waterhouse (1955) extended work by Rayleigh (1964) and confirmed experimentally that the power output of a source is affected by the presence of boundaries, for example the walls in a room. The effect of this is plotted in Figures 6.60 and 6.61 for two different boundary conditions. In one case, all the dimensions are the same (Figure 6.60); in the other, they are different to minimize the effects (Figure 6.61). It does not matter from which surface a speaker has a particular spacing. However, it is important that the dimensions are in the correct ratio. Note that in these graphs, the x-axis is the number of wavelengths with respect to the distance x from the boundary. This is analogous to frequency but scaled as with respect to distance. Thus if x equaled 1 meter, a value of 1 on the x-axis would correspond to a wavelength of 1 meter (344 Hz); if x equaled half a meter, a value of 1 on the x-axis would correspond to a wavelength of half a meter (688 Hz), and so on. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2134
Categorization
- QUESTION: How large is the boundary effect on power output in practice — worth chasing the Waterhouse and Rayleigh magnitude figures.
- DEFINE: The distance-to-boundary axis is frequency rescaled by distance, so the same curve describes different frequencies at different spacings.
- XREF: Connects to the book’s earlier chapters on boundary loading and loudspeaker directivity. — connects to: A reflecting wall doubles total sound power output from any source; Passive devices and even walls can amplify sound without power; Wall proximity alternately boosts or suppresses a source depending on phase. (+12 more)
- corroborated: 4 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2134; David Howard, Jamie Angus, coustics and Psychoacoustics, 2182