system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If 90dB is approximately the volume of a hairdryer and 90dB is the maximum volume for car exhausts, why do many cars sound louder than a hairdryer?
gpt
Measurements of soundpressure are not always taken at the same distance, but rather at a distance that makes sense. For example, a hairdryer is close to your ears when used, so it would be odd to measure it from two meters away. Likewise, nobody is anywhere near a jet plane when it takes off, so you wouldn't take a measurement from 10 cm away.

And this makes quite a big difference, as each time you double the distance from the microphone to sound source, measured sound pressure will decrease by (ideally) 6 dB.

So in this case, the measurement for the hair dryer is probably taken a lot closer to the measurement of the car's exhaust, which means that the exhaust would be quite a bit louder if the distance is equal.