@@MichaelCurtisAudio I think basically everybody in audio have this misconception, i only figured it out when learning photography where per doubling of the distance light loses two 'stops' (each stop being a halving) 😅
The inverse-square actually means that double distance will make the sound 1/4 as loud. At triple distance, it will be 1/9 as loud. Inverse-square refers literally to 1/r^2 What's happening here is that decibels are a logarithmic unit, meaning that each unit change stands for a multiplication of intensity, not an addition. The -6 dB between mics means that each mic is detecting 25% of the sound intensity of the others.
Actually it would, but obviously at a much smaller scale. If you consider your AirPods as an example, moving them just 1mm out of your ear it will greatly impact the audio volume. It’s the same with all speakers, but 1mm at this scale would be inside the cone movement, that being said physics is physics.
@@mitas3484 I am not teasing you, I really want to understand this. If I take my 1mm as reference point and double that 10 times I would be 1.024mm away, so roughly 1 meter /3 feet away. -60dB would be practically nothing. So. You did your video with feet since you are in the US. I am used to metric, so how do I adjust to that?
@@vanRossi it’s physics, so it’s independent of measurement type. You can use 1 meter to 2 meter, and 2 to 4 meter. Each doubling will see -6 dB decrease. In your example, try turning up your headphones to max volume and put a db meter inside. It may measure 110 db at 1mm, and may be almost exactly 50db at 1 meter away. If you measure a speaker at 1 meter, and double it to 2 meter it would be -6db, and this is a logarithmic scale. So the further away you get, the less impact on volume it will have. This is why you sometimes can hear concerts from kilometers away.
This might not be intuitive because arrays of speakers must be summed across the field of projected sound. Isolated sound could (theoretically) be quieter. This might be how you're thinking it's not intuitive. Things get complicated when variables are maxed out or minimized.
This is true for a point source and in the far field you can consider a speaker a point source. This means you should preferably at least have a 5 times distance from a speaker compared to it's diameter. For a woofer with a 10cm diameter this will work going from 1m to 2m. For an 21" woofer, you'll barely measure a difference going from 10cm to 20cm. So for it to work on a mm scale you should have a point source smaller than about 0.2mm. For speakers with multiple drivers the far field would be about 5 times the longest distance between driver edges. With 15m high line arrays the droppoff is also not 6dB per doubling until you're 30-50m away due to the accoustic coupling which makes it act more as a line source rather than a point source.
Actually the energy becomes one fourth, it's the sound pressure level that becomes a half
Looking for this, thank you for educating!
Great point, thanks for the clarity on word choice.
@@MichaelCurtisAudio I think basically everybody in audio have this misconception, i only figured it out when learning photography where per doubling of the distance light loses two 'stops' (each stop being a halving) 😅
The inverse-square actually means that double distance will make the sound 1/4 as loud. At triple distance, it will be 1/9 as loud. Inverse-square refers literally to 1/r^2
What's happening here is that decibels are a logarithmic unit, meaning that each unit change stands for a multiplication of intensity, not an addition. The -6 dB between mics means that each mic is detecting 25% of the sound intensity of the others.
well yea but 25% sound intensity does not mean it will be 1/4 as loud
How do you do your subtitles
We lose three quarters not one half. If you double the radius of a sphere its surface increases four times.
To what reference? Let's say I am one millimeter away from the speaker and I double the distance to two millimeters, this is obviously not -6dB?
Actually it would, but obviously at a much smaller scale. If you consider your AirPods as an example, moving them just 1mm out of your ear it will greatly impact the audio volume. It’s the same with all speakers, but 1mm at this scale would be inside the cone movement, that being said physics is physics.
@@mitas3484 I am not teasing you, I really want to understand this. If I take my 1mm as reference point and double that 10 times I would be 1.024mm away, so roughly 1 meter /3 feet away. -60dB would be practically nothing. So. You did your video with feet since you are in the US. I am used to metric, so how do I adjust to that?
@@vanRossi it’s physics, so it’s independent of measurement type. You can use 1 meter to 2 meter, and 2 to 4 meter. Each doubling will see -6 dB decrease.
In your example, try turning up your headphones to max volume and put a db meter inside. It may measure 110 db at 1mm, and may be almost exactly 50db at 1 meter away.
If you measure a speaker at 1 meter, and double it to 2 meter it would be -6db, and this is a logarithmic scale. So the further away you get, the less impact on volume it will have. This is why you sometimes can hear concerts from kilometers away.
This might not be intuitive because arrays of speakers must be summed across the field of projected sound.
Isolated sound could (theoretically) be quieter. This might be how you're thinking it's not intuitive. Things get complicated when variables are maxed out or minimized.
This is true for a point source and in the far field you can consider a speaker a point source. This means you should preferably at least have a 5 times distance from a speaker compared to it's diameter. For a woofer with a 10cm diameter this will work going from 1m to 2m. For an 21" woofer, you'll barely measure a difference going from 10cm to 20cm.
So for it to work on a mm scale you should have a point source smaller than about 0.2mm.
For speakers with multiple drivers the far field would be about 5 times the longest distance between driver edges.
With 15m high line arrays the droppoff is also not 6dB per doubling until you're 30-50m away due to the accoustic coupling which makes it act more as a line source rather than a point source.
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