Fireplace sounds
A low roar with sharp crackles over it, each one scheduled at an irregular interval so the fire never falls into a rhythm. The roar is filtered noise; the crackles are short bursts with a fast decay.
The roar is easy, the crackle is the whole problem
The continuous part of a fire is straightforward: brown noise through a low-pass at a few hundred hertz, with a slow breath on it so the flame appears to rise and settle. On its own it is convincing for perhaps ten seconds, at which point you notice you are listening to a rumble and not to a fire.
The crackles are what make it a fire, and they cannot be produced by any repeating process. Each one here is a very short burst of band-passed noise centred around 2.2 kHz with an exponential decay of about eighty milliseconds — quick enough to read as a snap rather than a thump. Longer decays are the giveaway of a synthetic fire: real crackles are almost instantaneous.
The timing is the part that took the most care. Crackles arrive at intervals drawn from a seeded random sequence, spread between roughly a third and one and a half times the mean gap, and each one gets its own loudness. Evenly spaced crackles are a metronome, and the ear identifies a metronome immediately even when the interval is a full second. Purely exponential timing has the opposite failure: it produces occasional long silences that sound like the fire has gone out.
Fire as a background sound rather than a spectacle
A fireplace is a poor masker and a good atmosphere, which is the reverse of the noise layers. Its energy is concentrated low, it has irregular sharp transients in the middle of the spectrum, and transients are exactly the thing that pulls attention rather than covering it. If your goal is to stop hearing a neighbour, this is the wrong layer.
What it is good for is making a quiet room feel occupied. It works particularly well underneath rain, which is the pairing most people arrive at on their own: the rain covers, the fire gives the impression of somewhere to be while it does. Adding a little wind on top of both is worth trying if the effect is too cosy to concentrate over.
Turning the fire slider up increases the crackle rate from about three a second to about twelve, and raises the burst level with it — the difference between embers settling and a freshly loaded log. Beyond about three quarters it becomes busy enough to be distracting, which is realistic and probably not what you want running for two hours.
Crackle rate across the slider
Each crackle is a short burst of band-passed noise with the decay shown. The rate is a mean, not a metronome: individual gaps are drawn from a seeded random sequence.
| Slider | Crackles | Decay | Character |
|---|---|---|---|
| 0% | 3 /s | 80 ms | Embers settling |
| 25% | 5.25 /s | 80 ms | A fire that has burned down |
| 50% | 7.5 /s | 80 ms | Steady, comfortable — the default here |
| 75% | 9.75 /s | 80 ms | A freshly loaded log |
| 100% | 12 /s | 80 ms | Busy enough to be distracting |
Common questions
Why do the crackles sound irregular?
Because they are. Each gap is drawn from a seeded random sequence rather than a fixed interval, since evenly spaced crackles are recognised as a metronome within a few seconds even at slow rates.
Can I have the fire without the crackle?
Not from the fire slider, but brown noise at a low setting with a touch of wind gives a similar continuous roar without any transients, and it masks considerably better.
Does this work as background sound for a video call?
It is a poor choice: the transients are in the same range as speech and noise suppression on most call software will try to remove them, producing odd artefacts. A steady layer such as pink noise behaves far better.