That LOUDNESS Button! August 2025

The most misunderstood feature on any audio product is the loudness switch or button. Loudness was derived by the research into making a good telephone (The handset one with both the receiver and transmitter in one piece) which resulted in the Fletcher-Munson curve. 

It was discovered that human hearing is not flat (equal) across all frequencies, assumed to be 20 to 20,000 Hz, but has curve across the frequencies with less perception at BOTH low and very high frequencies, particularly at low volumes.  This was used in the design of the original handset dial telephone.

Now, there is not one curve but many based upon decibel levels or how loud it is.  Almost all manufacturers produced a loudness button with a sort of one size fits all and the boosts varied between manufacturers.  

The only company that actually tried to get this right was Yamaha with their variable loudness.  You may recall seeing their loudness control with the numbers 1 thru 10. That would allow the user to change the loudness based upon the volume of the system.  This was actually a promoted feature but even this attempt was basically misunderstood.

Unfortunately, the loudness control became synonymous with bass boost and away it went. Wanted more thump, press the loudness. By the way, I don't think anyone really addressed the human weakness at the other end of the spectrum, treble. 

So now we come to audio products that do not have a loudness button.  This is where misunderstanding really comes into play. Human speech is typically between 55 to 65 db.  If you look at the curve, a loudness button does have some use. However, most people don't listen at that level but, higher.  Put into perspective, 90db is that of a lawnmower, a car horn at 10', or a shouting conversation.  People often listen at 70 to 80 db where the curve begins to flatten out. At 90, well, it is a lot flatter.  But a switch in the signal path is typically not harmless.  So, a number of manufacturers recognizing the incorrect use of the loudness button and the risk to accuracy, have chosen not to provide one at all.  For most, this is not a real issue.  For some, well, they rather cling to it as a bass boost.  

Now, recognizing that not everyone perceives sound the same way, particularly as we age, well, some equalization may be proper.  Life's experiences also dramatically affect hearing.  Constant loud noise at work can be a contributory factor in hearing deficiencies.  Even illnesses can affect life-long hearing.  So, it is not necessarily age dependent but typically it is. 

I thought it would be useful for all to understand a bit more about loudness and if you are interested, look up the Fletcher-Munson curve. 

-Lou