Noise vs Sound

All the way through this site you'll see me talk about 'noise' rather than 'sound' - is that important? 

For science types yes, there is a difference between the two terms and they will always, for example, refer to a 'noise meter' as a 'sound level meter', and that is technically the correct terminology as the meter is measuring sound, or even more accurately, pressure. That's what a noise meter actually measures - pressure in the air, and we use decibels as the scale for that. That's why you will see most noise meters advertised as 'sound level meters'.

Normal people however just use the term 'noise' and in this usage 'noise' makes no detrimental difference at all.

Sound Pressure Level (SPL) vs. volume

Human ears hear pressure, not volume, so technically a noise meter is measuring the 'sound pressure level' and noise obsessives often refer to this, whereas people who can go out in daylight and don't sleep with their favourite noise meter under their pillow just call it the 'volume of the noise'. Generally volume does increase with increasing pressure so when we say something has a noise level of 80dB that's technically a SPL of 80 dB and not a volume of 80dB. But, taking popular understanding and common use of the terminology it may as well be 'volume' and is what everyone else understands it as.

If you want more, I like this website's explanation of sound versus noise and what noise meters actually do - Explain That Stuff.