6 ms·

Same question about how loud it is. Wikipedia says thermoacoustic engines work at 180db, which is the sound of a pound of TNT being detonated 15 feet away.

pjerem 4y ago
> 180db, which is the sound of a pound of TNT being detonated 15 feet away. Sounds like that can be a bit annoying
- elliottkember 4y ago
  Fortunately, they're only annoying for a very short time
  - brnt 4y ago
    Plus, it'll be the last time ever you hear anything annoying at all.
    - magnetic 4y ago
      Not quite. After an acoustic trauma, especially bad enough to degrade your hearing, there is a good chance you will be gifted with life-long Tinnitus.
      - missedthecue 4y ago
        I think he's insinuating you're getting blown up. Guaranteed tinnitus cure
      - hinkley 4y ago
        It can also stop your heart.
- _eht 4y ago
  And warm!
dcroley 4y ago
Equium claims that the heat pump system is completely silent, despite the use of a speaker to generate the acoustic wave. The level of noise is reportedly lower than 30 dB – the equivalent of a whisper. “The sound our system produces stays confined inside the core, so you cannot hear it from outside,” said Loyer.
- arsalanb 4y ago
  I imagine this is possible because of better modulation of the acoustic and pressure controllers to minimize energy loss..
- waste_monk 4y ago
  My traditional heat pump (using R744) claims to produce about ~37dB, and while I have not measured it I can say I would not be able to hear it over a light breeze while standing right next to the thing, let alone inside the house with a wall in the way. To be even quieter than that is remarkable, IMO.
  - leguminous 4y ago
    I'm curious, where did you get a heat pump that uses R744? As far as I know, none of the major manufacturers offer one for residential use. I'm also curious about how well it works for you.
    - Danieru 4y ago
      It is super common in Japan for domestic hot water heating. It was pioneered by the government of Japan, electronic goods firms, and the power companies. You'll see them sold under the EcoCute name. Daikin, Panasonic, and Corona (no relation) make them. They get used for homes meant to only have water and electricity hookup, called "all electric" homes.
    - waste_monk 4y ago
      We have this thing https://www.sanden-hot-water.com.au/specifications/ https://www.sanden-hot-water.com.au/specifications/ IIRC with a 300L tank. It was quite a nice upgrade from our old 1960's era 2-phase instant hot water unit that was slowly failing - cold showers in winter are not fun. As user Danieru replied the heat pump is a a Japanese import (although the tank and rest of the system is locally made).
arsalanb 4y ago
Probably not. A similar acoustic heat pump company (https://www.blueheartenergy.com/ourtechnology https://www.blueheartenergy.com/ourtechnology) claims 30 db, so this is probably going to be in the ball park.
MayeulC 4y ago
Meh. This is a pressure wave. I wouldn't be surprised if tapping your finger on the table creates more pressure than that. Or hammering a nail, at least¹. Even your TNT figure has a distance indication. Pressure decreases with the square of the distance when it dissipates as a sphere. Doubling the distance = -6 dB ¹ 20*log(k)=180 => k=1e9, factor to reach between rest state and max pressure, I think.
- Godel_unicode 4y ago
  Is it? Doesn't Hopkinson–Cranz scaling mean that it would decrease at the cube of distance?
- WJW 4y ago
  Tnt exploding at 15 feet is definitely still a problem for living things. With regards to the article, by confining the pressure wave to a tube you effectively keep the surface area of the wavefront constant and so dissipation is much less of an issue.
- nautilius 4y ago
  This makes no sense. Of course sound is a pressure wave - but so is being hit by a nuclear blast wave (after the initial flash). Obviously, the magnitude plays the decisive role here and not it being a pressure wave.
deleted 4y ago
[deleted]
nickpinkston 4y ago
You're thinking of the decibels as measured from the exterior, but this likely refers to the decibels as measured at the point of constructive interference of the waveform in the chamber - ie the method of action of this heat pump. Those decibels then turn into heat, not exterior sound. It's a really cool application of the ideal gas law: PV = nRT where the sound is really playing with the pressure (P) using sound so various parts of the chamber have different temperatures (T).

pjerem 4y ago

> 180db, which is the sound of a pound of TNT being detonated 15 feet away. Sounds like that can be a bit annoying

elliottkember 4y ago
Fortunately, they're only annoying for a very short time
- brnt 4y ago
  Plus, it'll be the last time ever you hear anything annoying at all.
  - magnetic 4y ago
    Not quite. After an acoustic trauma, especially bad enough to degrade your hearing, there is a good chance you will be gifted with life-long Tinnitus.
    - missedthecue 4y ago
      I think he's insinuating you're getting blown up. Guaranteed tinnitus cure
    - hinkley 4y ago
      It can also stop your heart.
_eht 4y ago
And warm!

dcroley 4y ago

Equium claims that the heat pump system is completely silent, despite the use of a speaker to generate the acoustic wave. The level of noise is reportedly lower than 30 dB – the equivalent of a whisper. “The sound our system produces stays confined inside the core, so you cannot hear it from outside,” said Loyer.

arsalanb 4y ago
I imagine this is possible because of better modulation of the acoustic and pressure controllers to minimize energy loss..
waste_monk 4y ago
My traditional heat pump (using R744) claims to produce about ~37dB, and while I have not measured it I can say I would not be able to hear it over a light breeze while standing right next to the thing, let alone inside the house with a wall in the way. To be even quieter than that is remarkable, IMO.
- leguminous 4y ago
  I'm curious, where did you get a heat pump that uses R744? As far as I know, none of the major manufacturers offer one for residential use. I'm also curious about how well it works for you.
  - Danieru 4y ago
    It is super common in Japan for domestic hot water heating. It was pioneered by the government of Japan, electronic goods firms, and the power companies. You'll see them sold under the EcoCute name. Daikin, Panasonic, and Corona (no relation) make them. They get used for homes meant to only have water and electricity hookup, called "all electric" homes.
  - waste_monk 4y ago
    We have this thing https://www.sanden-hot-water.com.au/specifications/ https://www.sanden-hot-water.com.au/specifications/ IIRC with a 300L tank. It was quite a nice upgrade from our old 1960's era 2-phase instant hot water unit that was slowly failing - cold showers in winter are not fun. As user Danieru replied the heat pump is a a Japanese import (although the tank and rest of the system is locally made).

arsalanb 4y ago

Probably not. A similar acoustic heat pump company (https://www.blueheartenergy.com/ourtechnology https://www.blueheartenergy.com/ourtechnology) claims 30 db, so this is probably going to be in the ball park.

MayeulC 4y ago

Meh. This is a pressure wave. I wouldn't be surprised if tapping your finger on the table creates more pressure than that. Or hammering a nail, at least¹. Even your TNT figure has a distance indication. Pressure decreases with the square of the distance when it dissipates as a sphere. Doubling the distance = -6 dB ¹ 20*log(k)=180 => k=1e9, factor to reach between rest state and max pressure, I think.

Godel_unicode 4y ago
Is it? Doesn't Hopkinson–Cranz scaling mean that it would decrease at the cube of distance?
WJW 4y ago
Tnt exploding at 15 feet is definitely still a problem for living things. With regards to the article, by confining the pressure wave to a tube you effectively keep the surface area of the wavefront constant and so dissipation is much less of an issue.
nautilius 4y ago
This makes no sense. Of course sound is a pressure wave - but so is being hit by a nuclear blast wave (after the initial flash). Obviously, the magnitude plays the decisive role here and not it being a pressure wave.

deleted 4y ago

[deleted]

nickpinkston 4y ago

You're thinking of the decibels as measured from the exterior, but this likely refers to the decibels as measured at the point of constructive interference of the waveform in the chamber - ie the method of action of this heat pump. Those decibels then turn into heat, not exterior sound. It's a really cool application of the ideal gas law: PV = nRT where the sound is really playing with the pressure (P) using sound so various parts of the chamber have different temperatures (T).