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Old 9th August 2005
Lives for gear

Originally Posted by Robobo1

Check out the Fletcher-Munson curves... notice that there is quite a boost (in relation to the frequencies preceding) from 8kHz up.

A little high frequency goes a long way.
You may not be looking at that quite right. That is for percieved equal loudness of the frequency spectrum. i.e. frequencies below 200hz require progressively higher SPLs to appear as loud as frequencies in the 2-6khz range. Same for high frequencies except for a little bump of sensitivity around 12khz. Above 15khz you can see our sensitivity starts to dramatically trail off. That print of the curve doesn't even plot the response. From this you can see why intelligibility has a lot to do with that 2-6khz sensitivity (hence telephones limited bandwitdth). You can test this yourself somewhat. Slowly sweep an oscillator through your best full range headphones or speakers while riding the gain at the same time. Try to keep everything at an equal loudness. You will find at those very low and high frequencies that you are turning the gain way up. I guess so much so that when you are way up in the above 10khz range if you were to leave the gain equal and sweep down into 2khz it would be uncomfortably loud. This is so very unscientific. Several things may be at play that may exaggerate the curve even more. Your current state of hearing (we tend to lose that way upper air gradually as we age even if we aren't blasting ourselves with 110db regularly), the transducer's (speaker, headphone) ability to reproduce the signal (hardly flat even on big buck monitors), and the acoustic environment if you're trying it in the open air with speakers. You get the idea. I seem to hear a lot of attention and discussion about high and low frequencies in audio production. Vintage hi-fi, recording gear and many of the recordings we love so much were made at a time and under practices that didn't really pay much mind to frequencies above 12khz.