Øyvind Kvålsvoll@kvalsvoll
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Quote from Øyvind Kvålsvoll on 22/03/2022, 03:41
Sound field properties and reflected sound
Measuring both spl and velocity, we can study how the sound field works in a room with reflected sound. We can find direction, we can observe how velocity changes in the time domain, compared to spl.
For an intro to what I am talking about, see the Sound field properties thread where there is a simplified explanation of what sound is and sound field properties.
In-room, we expect to see a velocity that matches the frequency response of the pressure in the plane normal to the speakers, and a reduction in velocity sideways and vertical. And the velocity in the normal plane should have a short decay, while side and vertical should start at a reduced level with slower decay.
Sound field properties and reflected sound
Measuring both spl and velocity, we can study how the sound field works in a room with reflected sound. We can find direction, we can observe how velocity changes in the time domain, compared to spl.
For an intro to what I am talking about, see the Sound field properties thread where there is a simplified explanation of what sound is and sound field properties.
In-room, we expect to see a velocity that matches the frequency response of the pressure in the plane normal to the speakers, and a reduction in velocity sideways and vertical. And the velocity in the normal plane should have a short decay, while side and vertical should start at a reduced level with slower decay.
Øyvind Kvålsvoll@kvalsvoll
528 PostsTopic Author
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Quote from Øyvind Kvålsvoll on 22/03/2022, 03:41
Measured spl and velocity in on-axis, sideways and vertical directions:
Velocity measurements are valid up to 1KHz, and there is a high noise level at very low frequencies.
Measured spl and velocity in on-axis, sideways and vertical directions:
Velocity measurements are valid up to 1KHz, and there is a high noise level at very low frequencies.
Øyvind Kvålsvoll@kvalsvoll
528 PostsTopic Author
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Quote from Øyvind Kvålsvoll on 22/03/2022, 03:43
Decay for spl and velocity:
Decay for spl and velocity:
Øyvind Kvålsvoll@kvalsvoll
528 PostsTopic Author
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Quote from Øyvind Kvålsvoll on 22/03/2022, 03:43
Waterfall for spl and velocity:
Waterfall for spl and velocity:
Øyvind Kvålsvoll@kvalsvoll
528 PostsTopic Author
AdminCompany InsiderModerator
Quote from Øyvind Kvålsvoll on 22/03/2022, 03:44
From this, we can see:
- Velocity on-axis dominates early in time, and then drops off fast.
- Velocity in side and vertical directions are delayed, because they are a result from reflections that will be delayed in time.
- At low frequencies below 80hz, room reflections dominate and creates a situation where early sound velocity direction is determined by reflections.
- Very early sound is dominated by the direct sound and has a dominant direction on-axis, and the decaying room contribution has more equal and overall lower velocities in all directions.
This correlates well with theory. Early sound is directional, while reflected decaying sound has no distinct direction and is more diffuse.
From this, we can see:
- Velocity on-axis dominates early in time, and then drops off fast.
- Velocity in side and vertical directions are delayed, because they are a result from reflections that will be delayed in time.
- At low frequencies below 80hz, room reflections dominate and creates a situation where early sound velocity direction is determined by reflections.
- Very early sound is dominated by the direct sound and has a dominant direction on-axis, and the decaying room contribution has more equal and overall lower velocities in all directions.
This correlates well with theory. Early sound is directional, while reflected decaying sound has no distinct direction and is more diffuse.
