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The Fletcher-Munson Curve: What It Is & Why YOU Need To Master It

fletcher munson curve
If you want your music to sound awesome when its cranked up to 11, then you need to know about the Fletcher-Munson curve. We break it down in simple terms.

Musicians constantly deal with technical terms and equipment names that are confusing for the layperson.

Add “Fletcher-Munson Curve” to the list.

It’s confusing at first, but once you understand it you really see its importance.

But first, are you like me?

I love Loud Music

I love listening to music at loud volumes. It’s totally immersive and I can really feel it. I’m pretty sure you like nodding your head along to a good track, too, as you crank the volume and feel the beat.

But believe it or not, the volume at which you listen to music can have an effect on what you’re hearing.

This is what the Fletcher-Munson curve is all about.

What is the Fletcher-Munson Curve?

The Fletcher-Munson curve illustrates the human ear’s sensitivity to different frequencies at different volumes.

In simpler parlance, your brain perceives audio frequencies differently as they get louder.

  • At low volumes, low-range and high-range frequencies sound less prominent compared to mid-range frequencies.
  • At high volumes, mid-range frequencies sound less prominent compared to low-range and high-range frequencies

This is just an effect, though. The actual volume of your mix is the same no matter what. It’s just a question of perception.

But as is often the case in life, perception is reality when listening to music.

Why does this happen?

Science and biology time!

The difference in the apparent sound of a mix when you’re listening at different volumes is thanks to how the human ear works.

The ear senses pressure differences above and beneath atmospheric pressure. A sound wave that enters the ear canal exerts pressure on your eardrum. This pressure is constantly changing as the sounds you hear change, but the pressure on the opposite side of the eardrum remains constant at atmospheric pressure.

This difference in pressure between the two sides of the eardrum causes the eardrum to vibrate, which is transmitted to the inner ear. The inner ear is filled with fluid, and the movement of this fluid causes hair cells in the inner ear to be disturbed. This transmits nerve impulses to your brain, which the brain translates into sound as we perceive it.

To summarise:

  • Sound waves put varying degrees of pressure on your eardrum.
  • Changing pressure causes your eardrum to vibrate.
  • Eardrum vibrations are transmitted to the fluid-filled inner ear.
  • Hair cells in the fluid-filled inner ear sense the vibrations and transmit nerve impulses to your brain.
  • Your brain interprets these nerve impulses as sound.

While the biological know-how of how the ear works is certainly interesting, the main reason I mention it is because the ear is not equally sensitive to all frequencies in the range of audible sound.

Let’s take a look at this curve

Full disclosure: The curve can be a little confusing. But any guide to the Fletcher-Munson curve needs to actually show you the curve, right?

Here it is.

fletcher munson curve
The Fletcher Munson Curve is also called the Equal-Loudness Contour is a measure of sound pressure over the frequency spectrum. (Source)

You don’t need to understand this curve!

All you need to understand is what this curve means for you (and your audience) when you’re recording your mix.

What does this mean when I’m recording my mix?

Let’s think about your listeners for a second.

All good mixes have something in common: They achieve the ideal balance of frequencies that sounds great to their audience.

Let’s say you’re mixing a track. You listen to it at a lower volume because you’re in your studio wearing headphones. You decide that the highs and lows of the track could be boosted for it to sound better, so you boost them. Your track sounds phenomenal and you high-five yourself before closing shop for the day.

The next day, you’re listening to the same track, only you listen to it at a high volume on your studio monitors. The highs and lows sound overpowering, so you cut them down.

And with that, you’ve come full circle, right back to where you started.

Well, which version was better?

How to use the Fletcher-Munson curve to your advantage

When someone’s listening to a mix at a lower volume, odds are that they’re probably not giving it their full attention. They’re working on their computer or doing the dishes or whatever. Something else is in the foreground.

But when they’re playing your mix at full blast, it means that they’re definitely paying attention.

You want your mix to sound best when your listeners are giving it their complete focus, which is when they’re playing it loudly.

The Radio Test

Imagine your audience is listening to your new song on the radio. They like what they’re hearing, so they crank the volume up and it sounds fantastic.

Imagine if the reverse happened.

They love what they hear so they crank it up only for it to sound distorted. Not at all like what you intended.

Guess who won’t be listening to your track again?

You want your music to sound its best at loud volumes because that’s when most people are really listening to it.

And to achieve that, you have to equalize it at higher volumes. Not the max volume perhaps, but at a volume which you’d comfortably listen to it in reality.

Remember, if your lows and highs drop off a little when the volume is low, it might not sound the best but it won’t sound awful either. It’ll just make your audience want to turn the volume up.

That’s all you need to know about the Fletcher-Munson Curve and what it means for your music. Now go forth and mix your music with precision!


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