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).

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.

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

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.

> 180db, which is the sound of a pound of TNT being detonated 15 feet away.

Sounds like that can be a bit annoying