6 ms·

As far as deep bass goes, this won't hinder that - since bass waves have too high of a pressure to not pass through the object. The most effective material is

As far as deep bass goes, this won't hinder that - since bass waves have too high of a pressure to not pass through the object. The most effective material is high mass and flexible, like cork or hemp crete. Bass-traps also exist, they eat up the energy of sound pressure and are usually large tubes and many of them are needed to make a difference. So there's a reason that this test is on high-frequencies, not low ones. EDIT: Fine, down-vote me if you want but it doesn't make it less true [1] [1] https://www.acousticfields.com/how-do-you-stop-low-frequency-issues-in-a-small-room/ https://www.acousticfields.com/how-do-you-stop-low-frequency...

simonebrunozzi 8y ago
I am surprised to read that you were downvoted by some. Even if you are completely wrong (I have no idea, I am not a sound engineer), you are trying to provide an opinion and I would simply debate it with you, rather than downvoting.
- deleted 8y ago
  [deleted]
- BossingAround 8y ago
  Lately, I have noticed a lot more downvoting going on than I was used to. Maybe a confirmation bias on my part, but sad nevertheless... I'd use downvoting only for submissions that are harmful.
  - vanderZwan 8y ago
    The longer this website is around, the more people there will be with enough karma to be able to downvote in the first place. Perhaps that explains the shift you've seen? If so then perhaps the weighing of upvotes/downvotes should be adjusted to reflect that change in voting power?
fulafel 8y ago
The article mentions on one hand a high pitched note, but on another hand enough bass to see the subwoofers play it: "Standing in the room, based on your sense of hearing alone, you’d never know that the loudspeaker was blasting an irritatingly high-pitched note. If, however, you peered into the PVC pipe, you would see the loudspeaker’s subwoofers thrumming away."
- tmikaeld 8y ago
  I assumed that this was the interviewers observation and not a fact, because even a mid-range driver would be moving visibly. Considering the size of the tube, this is certainly not a driver big enough to go to lower frequencies. (Specialized drivers at 4" can go down to 25hz though)
IshKebab 8y ago
You might be being downvoted because you've confused frequency with amplitude. Bass means low frequency / long wavelength. It doesn't say anything about amplitude / pressure.
- atoav 8y ago
  To get the same (perceived) amplitude a low freuquency wave needs much more power than a higher frequency one. In a speaker most power is used in the low end while the tweeters use just a fraction of it. This means that given any kind of regular music played on this speaker the created air pressure differences will be much higher for the bass frequencies than for the treble frequencies. On top of that the difference in wave length also changes how it interacts with materials. The long bass wave bends around corners and goes through walls (which is why you can hear them two rooms over), while the shorter treble wave is bascially reflected by even a thin wall and looses energy fast in free air.
- TheOtherHobbes 8y ago
  Bass carries more energy, and the waves have higher pressure as well as a longer wavelength. You can attenuate treble with a sheet of toilet paper, but you need a lot of mass to stop bass of equivalent nominal level.
  - hexane360 8y ago
    Your result is correct but your explanation is all kinds of wrong. First, shorter wavelength waves have higher energy. Second, amplitude doesn't cause the difference here. Even if you needed 1000W of bass to get the same effect as 10W of treble, 50% attenuation of bass would sound the same as 50% attenuation of treble. The real difference is that waves are attenuated much more by objects larger than their wavelength.
    - TheOtherHobbes 8y ago
      Sound isn't light. If you have source for your suggestion that shorter wavelengths of sound carry more energy, I'd be curious to see it. And no, the real difference isn't that waves are attenuated much more by objects larger than their wavelengths. A 200m^2 sheet of paper will still attenuate treble and be completely transparent to bass. The real difference is that bass damping requires a combination of size, raw mass, and permeability. It's true that a tiny stick of a bass-damping material will do nothing to stop bass, but it's also true that giant bass traps - like the ones used in studios - will stop treble dead, but their effectiveness at bass frequencies depends entirely on size, thickness, and the material they're made of. A concrete wall has plenty of mass but no permeability, so it's a good reflector at most frequencies. Bass traps use permeable materials like mineral fibre which have no effect in thin slices, but they're made thick enough to provide enough mass to damp the pressure oscillations.
abainbridge 8y ago
> The most effective material is high mass and flexible, like cork or hemp crete. Those materials work by providing a physical barrier. This invention is not comparable because it appears to allow air to flow down the pipe but (somewhat) prevents the sound. I guess it should be compared to the performance of acoustic ducting or inline silencers (ie like in a car exhaust).
- tmikaeld 8y ago
  That's why i mentioned bass-traps, which can be done with cheap PVC pipes in the corners of a room.
  - abainbridge 8y ago
    I still don't understand your point. In the scenario in the article, you've got some noise coming down a pipe and the invention attenuates it. By "PVC pipes in the corner of a room", it seems like you are talking about a way to remove resonant frequencies from a room - as some folks do to improve the acoustics of a room for a hi-fi setup. In the scenario in the article, the noise is in a pipe, not in a room.
    - tmikaeld 8y ago
      I noticed that people assumed that this invention could block any sound, but it can only block specific frequencies, so that's why i pointed out that low frequencies can't be blocked - the test itself doesn't mention low frequencies. It wasn't a complaint to the invention itself, which is certainly promising for blocking sounds in ventilation while keeping airflow. PVC pipes trap low frequency sound by eating up it's energy and since low frequencies penetrate solid objects, resonant sound is what people are most annoyed by and those are reproduced in corners of a room - which is a good target for PVC bass traps to cancel out the bass. When it comes to high frequencies, they bounce easier, so it's more about building a "maze" of surfaces for the sound to bounce on until it looses it's energy, which seems to be exactly what they do in the article, they keep bouncing the waves backwards until they die out and it's quite clever.
edejong 8y ago
The article mentions using feno-like resonance to transform the frequency response (and phase). The effects of this are localized to a frequency-band around 440 Hz. Interestingly, this is a similar effect as mie-scattering. Therefore, I am not sure the common knowledge of bass-traps and heavy materials for muffling sounds are actually applicable here. I suggest reading the article and studying feno resonance.
- Gatsky 8y ago
  It's Fano resonance.
- tmikaeld 8y ago
  And if I'm not mistaken, Fano resonances only work in a controlled environment like headphones (noise cancelling). My comment wasn't a comment to the test in the article, but the expectations of the article - that any sound can be blocked, the writer is implying that this can be built into anything "a quieter world", which is not true for low frequencies which can't cancel itself out (without a very controlled environment like two subs of the same size in a cabinet, or an MRI machine) simply because it passes through objects and don't bounce. I've seen noise cancellation concepts for the real world before, where a unit is placed on a window to cancel out outside noise by matching the vibrations of the sound. In practice however, the sound waves are not predictable without a controlled environment, so it's just vaporware/concept [1]. [1] https://www.youtube.com/watch?v=Mv6sBuwzLhk https://www.youtube.com/watch?v=Mv6sBuwzLhk
bloopernova 8y ago
Thank you for posting about the bass trap, I had never heard of it before and am enjoying spending time learning about it (and the other sound-dampening materials you mentioned) This makes me wish I could put some bass traps in the wall between one neighbour and me, and something like hemp crete to drown out the sound of the screaming kids from another neighbour!
- georgn 8y ago
  By all means, read up on bass traps... but be aware that posts about bass traps imply a fundamental misunderstanding of what they do (perhaps I'm misreading). The problem: a speaker in a room produces sound, that sound is reflects by the walls. Those reflections will vary WRT phase of the original sound and causing something called comb-filtering (some frequencies will be louder because the reflections are in phase and amplify -- others will be 180º out of phase, resulting in a complete cancellation of those frequencies). Solutions: sound attenuating material at the edges of a room to interfere with the _reflections_ and this reduce or eliminate comb-filtering. The goal is to improve the listening experience _inside_ the room. Acoustic treatment does almost nothing to help your neighbours.
rdiddly 8y ago
It's not a question of pressure; a wave has whatever pressure it has. It's a question of frequency (wavelength). Just like a flute can't make tuba sounds, a small one of these can't attenuate large wavelengths. But they make larger flutes that can play lower tones. Could you not just make one of these arbitrarily large to handle an arbitrarily low frequency?

simonebrunozzi 8y ago

I am surprised to read that you were downvoted by some. Even if you are completely wrong (I have no idea, I am not a sound engineer), you are trying to provide an opinion and I would simply debate it with you, rather than downvoting.

deleted 8y ago
[deleted]
BossingAround 8y ago
Lately, I have noticed a lot more downvoting going on than I was used to. Maybe a confirmation bias on my part, but sad nevertheless... I'd use downvoting only for submissions that are harmful.
- vanderZwan 8y ago
  The longer this website is around, the more people there will be with enough karma to be able to downvote in the first place. Perhaps that explains the shift you've seen? If so then perhaps the weighing of upvotes/downvotes should be adjusted to reflect that change in voting power?

fulafel 8y ago

The article mentions on one hand a high pitched note, but on another hand enough bass to see the subwoofers play it: "Standing in the room, based on your sense of hearing alone, you’d never know that the loudspeaker was blasting an irritatingly high-pitched note. If, however, you peered into the PVC pipe, you would see the loudspeaker’s subwoofers thrumming away."

tmikaeld 8y ago
I assumed that this was the interviewers observation and not a fact, because even a mid-range driver would be moving visibly. Considering the size of the tube, this is certainly not a driver big enough to go to lower frequencies. (Specialized drivers at 4" can go down to 25hz though)

IshKebab 8y ago

You might be being downvoted because you've confused frequency with amplitude. Bass means low frequency / long wavelength. It doesn't say anything about amplitude / pressure.

atoav 8y ago
To get the same (perceived) amplitude a low freuquency wave needs much more power than a higher frequency one. In a speaker most power is used in the low end while the tweeters use just a fraction of it. This means that given any kind of regular music played on this speaker the created air pressure differences will be much higher for the bass frequencies than for the treble frequencies. On top of that the difference in wave length also changes how it interacts with materials. The long bass wave bends around corners and goes through walls (which is why you can hear them two rooms over), while the shorter treble wave is bascially reflected by even a thin wall and looses energy fast in free air.
TheOtherHobbes 8y ago
Bass carries more energy, and the waves have higher pressure as well as a longer wavelength. You can attenuate treble with a sheet of toilet paper, but you need a lot of mass to stop bass of equivalent nominal level.
- hexane360 8y ago
  Your result is correct but your explanation is all kinds of wrong. First, shorter wavelength waves have higher energy. Second, amplitude doesn't cause the difference here. Even if you needed 1000W of bass to get the same effect as 10W of treble, 50% attenuation of bass would sound the same as 50% attenuation of treble. The real difference is that waves are attenuated much more by objects larger than their wavelength.
  - TheOtherHobbes 8y ago
    Sound isn't light. If you have source for your suggestion that shorter wavelengths of sound carry more energy, I'd be curious to see it. And no, the real difference isn't that waves are attenuated much more by objects larger than their wavelengths. A 200m^2 sheet of paper will still attenuate treble and be completely transparent to bass. The real difference is that bass damping requires a combination of size, raw mass, and permeability. It's true that a tiny stick of a bass-damping material will do nothing to stop bass, but it's also true that giant bass traps - like the ones used in studios - will stop treble dead, but their effectiveness at bass frequencies depends entirely on size, thickness, and the material they're made of. A concrete wall has plenty of mass but no permeability, so it's a good reflector at most frequencies. Bass traps use permeable materials like mineral fibre which have no effect in thin slices, but they're made thick enough to provide enough mass to damp the pressure oscillations.

abainbridge 8y ago

> The most effective material is high mass and flexible, like cork or hemp crete. Those materials work by providing a physical barrier. This invention is not comparable because it appears to allow air to flow down the pipe but (somewhat) prevents the sound. I guess it should be compared to the performance of acoustic ducting or inline silencers (ie like in a car exhaust).

tmikaeld 8y ago
That's why i mentioned bass-traps, which can be done with cheap PVC pipes in the corners of a room.
- abainbridge 8y ago
  I still don't understand your point. In the scenario in the article, you've got some noise coming down a pipe and the invention attenuates it. By "PVC pipes in the corner of a room", it seems like you are talking about a way to remove resonant frequencies from a room - as some folks do to improve the acoustics of a room for a hi-fi setup. In the scenario in the article, the noise is in a pipe, not in a room.
  - tmikaeld 8y ago
    I noticed that people assumed that this invention could block any sound, but it can only block specific frequencies, so that's why i pointed out that low frequencies can't be blocked - the test itself doesn't mention low frequencies. It wasn't a complaint to the invention itself, which is certainly promising for blocking sounds in ventilation while keeping airflow. PVC pipes trap low frequency sound by eating up it's energy and since low frequencies penetrate solid objects, resonant sound is what people are most annoyed by and those are reproduced in corners of a room - which is a good target for PVC bass traps to cancel out the bass. When it comes to high frequencies, they bounce easier, so it's more about building a "maze" of surfaces for the sound to bounce on until it looses it's energy, which seems to be exactly what they do in the article, they keep bouncing the waves backwards until they die out and it's quite clever.

edejong 8y ago

The article mentions using feno-like resonance to transform the frequency response (and phase). The effects of this are localized to a frequency-band around 440 Hz. Interestingly, this is a similar effect as mie-scattering. Therefore, I am not sure the common knowledge of bass-traps and heavy materials for muffling sounds are actually applicable here. I suggest reading the article and studying feno resonance.

Gatsky 8y ago
It's Fano resonance.
tmikaeld 8y ago
And if I'm not mistaken, Fano resonances only work in a controlled environment like headphones (noise cancelling). My comment wasn't a comment to the test in the article, but the expectations of the article - that any sound can be blocked, the writer is implying that this can be built into anything "a quieter world", which is not true for low frequencies which can't cancel itself out (without a very controlled environment like two subs of the same size in a cabinet, or an MRI machine) simply because it passes through objects and don't bounce. I've seen noise cancellation concepts for the real world before, where a unit is placed on a window to cancel out outside noise by matching the vibrations of the sound. In practice however, the sound waves are not predictable without a controlled environment, so it's just vaporware/concept [1]. [1] https://www.youtube.com/watch?v=Mv6sBuwzLhk https://www.youtube.com/watch?v=Mv6sBuwzLhk

bloopernova 8y ago

Thank you for posting about the bass trap, I had never heard of it before and am enjoying spending time learning about it (and the other sound-dampening materials you mentioned) This makes me wish I could put some bass traps in the wall between one neighbour and me, and something like hemp crete to drown out the sound of the screaming kids from another neighbour!

georgn 8y ago
By all means, read up on bass traps... but be aware that posts about bass traps imply a fundamental misunderstanding of what they do (perhaps I'm misreading). The problem: a speaker in a room produces sound, that sound is reflects by the walls. Those reflections will vary WRT phase of the original sound and causing something called comb-filtering (some frequencies will be louder because the reflections are in phase and amplify -- others will be 180º out of phase, resulting in a complete cancellation of those frequencies). Solutions: sound attenuating material at the edges of a room to interfere with the _reflections_ and this reduce or eliminate comb-filtering. The goal is to improve the listening experience _inside_ the room. Acoustic treatment does almost nothing to help your neighbours.

rdiddly 8y ago

It's not a question of pressure; a wave has whatever pressure it has. It's a question of frequency (wavelength). Just like a flute can't make tuba sounds, a small one of these can't attenuate large wavelengths. But they make larger flutes that can play lower tones. Could you not just make one of these arbitrarily large to handle an arbitrarily low frequency?