When you play your recording back it gets converted to analog voltage again, after which it gets amplified by the headphone amp (often around +50 - 90 dB) The zoom has a microphone which converts the sound pressure in the air to a certain electrical voltage, which then gets amplified by a preamp (which can give you anywhere from 0 or even -20 to 60-90 decibels in gain).Īfter that it gets turned into 1s and 0s (and the values become dBFS - computer decibels) The 40 dBs you read on the sound meter means that its 40 decibels above the approximate threshold of human hearing (0 would be nigh unnoticeable)(also a simplified explanation). 14 dB means that the signal is 14 dBs lower than the maximum a computer can "handle"or "comprehend", in simple terms. The dBs in audition are dBFS (decibel full scale). The input gain on your audio interface, the track fader, the master fader, the volume knob on your audio interface, the volume knob on your speakers (or headphone amp if you have one), etc. Those aren't even the minimums and maximums, but my point is that whatever correlation there may be between dB and dBFS is meaningless because there are numerous spots in the signal chain where you can turn the signal up or down. You could have a 40 dB sound and set your input gain so low that when it's converted into a digital signal, it's peaking at -40 dBFS, or set it so high that it's peaking at -1 dBFS. You could have a -14 dBFS signal, and once it's converted to sound, that sound could be 7 dB or 70 dB depending on where you set your volume knob on your audio interface. You touched on this in your comment, but it's important to note that when it comes to digital audio, there are many points in the signal chain that can make the signal louder or quieter before it turns back into sound coming out of your speakers or headphones. More detail than this is a bit beyond the scope of a reddit post, read up in a book like Modern Recording Technique by Miles Huber or the Yamaha Sound Reinforcement Handbook, or there's most likely a relevant article on Sound On Sound's web site. So we will be more interested in average readings over a short time to adjust for "sounds like" sound pressure levels. And there is also the additional complication that, while momentary peaks that are too high might cause digital clipping, that's not how our ears respond, and so that instantaneous peak might not even sound terribly loud. In actual practice, headphone levels might be set so that, when you monitor a recording, your maximum levels (peaks at 0dBFS) do not damage your hearing or even come anywhere close. You are not by any means alone in feeling confused by this! If you wanted to hear that recording at the actual level it sounded like you would have to set your playback amplifier for the headphones so that it SOUNDED LIKE 40 dBSPL when it hit your eardrum - this, too, is adjustable, but it's not super easy to measure accurately without specialized test equipment. How loud you hear in your headphones would depend on how your playback level is calibrated. So you have 14 more dB available for recording before you clip your peaks, and if you recorded "absolute silence" it would be 40 dB below that level, at -54dB (dBFS) on your level meter in the software, and 0dB (dBSPL) on your sound pressure level reading out in the world. On your recording software, this sound might register (depending on how your recording levels were set, they are adjustable) at a peak level of -14 dBFS. Here's an example: you record a sound out in the world somewhere and your peak SPL measurement is, let's say, 40 dBSPL. But you also have to make sure you are comparing apples to apples - peaks compared to peaks, averages compared to averages. Mixing the two systems, fortunately, is compatible - a dB comparison in one system will be able to be used in the other. 0dBFS means "0 dB Full Scale" and any level that can be recorded on that digital system will necessarily be below that full scale measurement so it will be a negative number. In software, the dB levels that you see are referred to the top end of the digital sampling system's capability. So you will get a positive number for any normal sound pressure you measure. That's a very very quiet level - basically the bottom of human hearing range. Your two readings are being compared to different reference levels - the "0 dB" in each system is different.Ī sound pressure level is a loudness measurement and its reference is 0dBSPL. A dB figure is ALWAYS compared to another level (a voltage or pressure.)
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