Could someone explain SPL to me?

[defeasible]

Hey guys, I figured out on the web that "SPL" means "sound pressure level," but I'm having a hard time figuring out what that exactly means. I know that it's generally better for a mic to have a higher sound pressure level, but what exactly will a higher sound pressure level get for you? Sorry for lambasting the forums with such a basic question.

 

[Track Rat]

Your understanding is a bit off. Sound Pressure Level is the sound wave measured at a given point in space. This more or less equates to loudness. It's not good to have as much SPL at the mic as possible as that buys you distortion. What's nice to have is a mic that's capable of handling high SPL for a given task, like recording drums or amplifiers (along with the rest of the recording chain).

 

[defeasible]

Ok, that makes much more sense. So SPL is not something that a mic has, but rather it's a term used to describe the level of sound a mic can handle without distortion. So a mic with a higher SPL will hander louder/higher sound pressures at a given instance. Sweet, thanks Mike.

 

[snow lizard]

SPL is useful for understanding a few different things in audio. The Fletcher Munson curves come to mind. A lot of people will say that mixing at around 85 dB SPL is a good idea because this is around the point where our ears frequency response flattens out.

I don't think I have it handy at the moment but there's a table in the Workers Compensation book that gives guidelines for what kind of sound pressure levels our ears can handle over given periods of time to enable us to select the right kind of hearing protection. As the SPL goes up, the ear's ability to defend against damage goes down for given periods of time. If you become overexposed, the ear's ability to perform critical tasks like mixing music is compromised until you have around 24 hours of quiet for the ear to adjust back to normal. Once you reach around 140 dB SPL this is somewhere around the sound level of sticking your head in the back side of a very large jet engine. Some microphones can handle this. A human would go deaf very quickly.

Condenser mics sometimes have something called a pad. There's a capsule that picks up the sound at a very low level and a head amplifier that boosts the level somewhat within the mic, before it goes to the preamp to come up to line level. Usually when using a mic like this in very close quarters to something really loud it's a good idea to use the pad. It drops the output of the head amp to keep it from distorting. Pads usually range from something like 10 to 20 dB.

A cheap handheld SPL meter is a handy thing to have.