How Loud Is a Motorcycle?

NIDCD publishes motorcycles and dirt bikes at 80–110 dBANIDCD.

Thirty decibels is an unusually wide published range, and it is not vagueness. It is the honest description of a category that contains a small commuter bike idling at a light and a modified machine at full throttle, heard from the saddle. At the bottom of that range nothing accumulates. At the top, minutes matter.

Where it sits against everything else

The bottom of the published band is quieter than a lawn mower. The top is above a concert. No single figure describes a motorcycle, and any page that gives you one has picked a point inside somebody else's range.

The check that works without equipment: at 85 dBA you have to raise your voice to be heard three feet away, and at 95 dBA you have to shoutNIOSH. Under a helmet at speed, neither is a test you can run — which is part of why riders systematically underestimate this one.

What decides where a bike lands

Throttle and speed, more than anything. The published range's top end is not an idling machine.

The exhaust. A stock system and a replacement are different acoustic objects, and the difference is usually the single largest factor a rider controls.

Where you are. The figure at the saddle and the figure on the pavement are different numbers, and published values rarely say which they describe.

Wind. This is the one riders miss. At road speed a substantial part of what reaches the ear inside a helmet is airflow rather than engine, and it rises with speed independently of what the bike is doing. A quiet bike ridden fast is not a quiet environment.

How long is a ride safe

Take the published range at both ends. Below 85 dBA the NIOSH table has nothing to say — its published figures start at 85 dBA for eight hoursNIOSH — so a quiet bike on a short trip is not the question.

Toward the top it changes fast, because the allowed time halves for every 3 dBNIOSH. At 100 dBA the whole daily allowance is a quarter of an hour, which is shorter than most commutes. That end of the scale is 100 dB.

The structural problem with riding is not any single trip. It is that a commute repeats — twice a day, most days — and NIOSH identifies repeated exposure rather than single events as the mechanism behind most noise-induced hearing lossNIOSH. A weekend ride and a daily commute at the same level are not the same proposition.

And the usual caveat, which cuts the same way it does everywhere on this site: the limit is occupational, and NIOSH says outright that it is not a recommendation for general-environment noiseNIOSH. A rider has no employer counting the hours, so borrowing the figure understates the case rather than overstating it.

What riders can actually do

Earplugs under the helmet. The single most effective thing, and the one most experienced riders converge on. The allowed time doubles for every 3 dB of reductionNIOSH, so even a modest reduction changes the arithmetic of a daily commute substantially. How much any particular pair gives is on the packet — this page is not going to invent a figure for it.

Speed. Since a large share of in-helmet noise is airflow, the level is partly a function of how fast you are going rather than of the machine.

The exhaust, if it is not stock. A replacement system is a decision about this, whether or not it was made for this reason.

Helmet choice and screen height also change the airflow picture, and they are worth comparing yourself rather than by specification — which is a comparison a rough reading can genuinely make.

What the neighbours and the street hear

A different question from the one above, and the one most searches for motorcycle decibels are actually about.

The published range describes the category, not a distance. A bike passing on the street delivers a short, loud event to everyone within earshot, and the thing that makes it a complaint is rarely the peak level — it is the hour, the repetition, and the fact that it arrives without warning. Sound at or below 70 dBA is unlikely to damage hearing however long it lastsNIDCD, and most pass-by noise arriving indoors is below that, which means a complaint about it is about sleep and quiet enjoyment rather than about hearing.

That is not a weaker complaint. It is a different one, and it is answered by local ordinances and vehicle noise rules rather than by any figure on this page — those rules exist, they vary enormously, and they usually specify a test procedure this site cannot reproduce.

Why published motorcycle figures disagree so much

If you search for a number you will find several, and they will not agree. All of the following are being measured by somebody, and they are different things:

The level at the rider's ear inside a helmet. The level beside a stationary machine. The level at a fixed distance during a standardised drive-by. The level inside a house as one passes. Each has a legitimate use and none converts into the others without information nobody publishes alongside the figure.

NIDCD's 80–110 dBA bandNIDCD is wide enough to cover most of them, which is exactly why it is worth quoting rather than a tighter figure from a source that does not say what it measured. When a page gives you a single confident number for a motorcycle, the first question is where the microphone was.

The same caution applies to figures quoted in arguments about exhausts. A number from a drive-by test and a number from beside the machine are not comparable, and a rider and a neighbour quoting different figures at each other are usually both right about different measurements. Establishing which one is being talked about settles more of those arguments than any additional decibel figure does.

Finding out where yours sits

The noise meter online here runs in the browser, which makes a rough answer available without buying anything.

The honest caveats are larger for this source than most. The reading is an uncalibrated estimate — sound apps have been found to scatter by roughly ±10 dB against a reference instrumentKardous & Shaw — and a phone input runs out of headroom somewhere around 100 to 105 dB, which is inside the published range for this category. A reading that stops responding at full throttle should be read as at least that.

Wind is the other problem. A phone microphone exposed to moving air reports the airflow across it, which is not what you are trying to find out. Any reading taken at speed on an open bike is measuring the wrong thing, and a stationary reading beside the machine is the only one worth taking with this equipment.

What that reading is good for, as everywhere on this site, is comparison: stock against replacement exhaust, idle against throttle, this bike against that one, taken the same way each time.

Nearby questions

For a machine published in a much narrower band and met by nearly everyone, see lawn mower dB.

For the other place a published range runs from the high nineties into the hundred-and-tens, and the one people attend on purpose: how loud is a concert.