[JohnR]

I think you're misreading the curve, or misunderstanding its intent. At 40 Hz, the threshold of hearing is 50 dB. That's a long way from zero, but still fairly quiet.

Put the same amount of power into a "flat" loudspeaker driven by a 3.5 kHz tone, what will the SPL be? Exactly the same - 50 dB. Same power, same SPL. It's just that it's easier for us to hear, because our ear is more sensitive at that frequency.

All these curves say is that in an isolated test, different frequencies require different SPL for us to "think" that they are the same loudness. But more importantly, as you move up the curves, the shape changes. That's why there is the old "loudness" button - to compensate for this effect.

Perhaps it is important to emphasize that these curves represent a characteristic of our ears, not our hifi systems. If I listen to an orchestra, I hear a certain spectral balance. If I listen to a recording of the same orchestra at the same volume, I hear the same spectral balance. Whatever it is that our ears are hearing, it is the same whether we are listening to the real thing or the recording, all other things being equal.

There is nothing to "debunk" here...

[a1p1]

JohnR and *Scotty*

I know that the Munson curve has nothing to do with amplification, all I was pointing out was, if the Munson curve was correct, it would take a staggering amount of amplication of the 44hz signal to be at the same spl as at 3.5khz.  Yet we do hear the bass at 44hz and at the same or near same spl's at 44hz and 3.5khz.   This in itself debunks the curve, at least to me it does.

I hope this clarify's this.   

Jim

Jim,
You are talking about two very different things.  Yes, the "Threshold" values shown in the Fletcher-Munson curves have nothing to do with your amplfiiers yet you bring up the amplfication needed to hear these two frequencies.  Your speakers are not your ears.  I'm not saying you can't hear 40Hz or hear a 3dB difference at 40Hz; again two very different questions versus the frequency sensitivity of the ear.  It is absolutely true that the human is not equally sensitive to all frequencies.  This is well established and accepted within the fields of audiology, acoustics, otolaryngology and has been for decades.  Much has to do with the middle-ear transfer function and pinna effects.   That's all I'll say as it seems you are looking for a fight, and don't quite understand the fundamentals or even what you were orignally asking. 

[JRace]

Jim this has been science fact for almost 80 years and has been researched to death.

Keep in mind that as the sound level increases the curve flattens.

3.5k Hz at 75db is equal to 45 Hz at 82db (roughly). Thats only 7dB of difference and when referenced to hearing thresholds ( and not amplifier power) that is not a big change.

What your hearing at your listening position is far removed from threshold testing done in a audiological setting, and you can not compare.

[Tyson]

Also, bass is not just about hearing, it's about feeling too.  Bass below 80 hz becomes more and more tactile, an important quality in music, and one reason why headphones will never give the same full musical presentation that full range speakers can.

[medium jim]

Guys:

I'm like a chess player baiting people into the wrong move, call it a gambit.  Here's a verbatim post from the "other" thread:

"To our dear bass obsession 'cult' members,

Before you want to add how many subs inside you home sweet home, making it look like a dump yard & a huge pain in the neck to every other homeate (unless you live ALONE), please understand how our ears sense bass frequencies.

From a Threshold of Hearing chart, it shows humans are most senstive to tones at about 3,500Hz (0dB reference) & least senstive to sub sub sonic bass is 20Hz (77dB) & below.

So for our ears to hear 20Hz as loud as 3.5KHz, the amps, including the power subs all add together, have to produce SPL 1,000,000 - 10,000,000 times loudness than 3.5KHz!!. If this physically possible, let alone hearing ability going down with age?

Take yr link of HiFi Zine as example, it recommends +/- 3dB at 44Hz,
44Hz needs the amps to generate over 50dB or over 100,000 times SPL LOUDER than 3.5KHz.

My question is: can our ears hear +/- 3dB SPL of  44Hz???

c-J"

I apologize for the round about way I presented my opinions, but it wasn't I who misunderstood the meaning of the Munson Curve and how it it relates to the real world. 

I guess what bothered me was said persons attitude of superiority and that us bass cult members were all idiots.  With that, please carry on

Jim

[srb]

Also, bass is not just about hearing, it's about feeling too.  Bass below 80 hz becomes more and more tactile, an important quality in music, and one reason why headphones will never give the same full musical presentation that full range speakers can.

True.  Deaf people can often feel the vibrations from recorded music and the majority of the time I would think they're feeling it from average systems that don't plumb the depths much below 40Hz.

Steve

[medium jim]

True.  Deaf people can often feel the vibrations from recorded music and the majority of the time I would think they're feeling it from average systems that don't plumb the depths much below 40Hz.

Steve

Steve, I agree that Bass and other frequencies can be felt. In fact, Kamaka Ukulele Company employs many deaf native Hawaiians to build their Ukes as their sense of touch and feel is amazingly adept to the vibrations given off.  This results in some amazing sounding Ukes.

http://www.kamakahawaii.com/about.html

Jim

[TRADERXFAN]

Also there is an effect of perception based on harmonics. i think its where a low tone will have harmonics with higher frequencies that we hear, more easily and our brain interprets the lower sound from the higher frequency harmonics. 
--found a link to this
http://en.wikipedia.org/wiki/Missing_fundamental

I read about this in regards to some dsp algorithm they were using to mimic lower frequencies in small systems like spherex that made things  sound deeper than they actually were being produced by the speaker,  by manipulating this effect with artificial modulations.

-Tony

[Chromisdesigns]

I've heard that enveloping bass that doesn't seem to be coming from the speakers.  The room even.  It's pretty elating.  Was it actually a part of the recording (i.e. in the music) or the speaker's output engagement with the room?  I suspect the latter.  Don't recall ever having heard it live.  What say ye?

Two counter-examples:  1) any outdoor Dead concert back when they were using the "Wall of Sound".  The bass was not only tight, it WAS all-enveloping.

2)  Bass fiddle live in a small venue.

[medium jim]

Two counter-examples:  1) any outdoor Dead concert back when they were using the "Wall of Sound".  The bass was not only tight, it WAS all-enveloping.

2)  Bass fiddle live in a small venue.

I agree about The Grateful Dead....not only was the wall of sound amazing, but so was Phil Lesh's bass playing!

Yes, bass can and is visceral and that is the joy of it....

Jim

[kevin360]

Also there is an effect of perception based on harmonics. i think its where a low tone will have harmonics with higher frequencies that we hear, more easily and our brain interprets the lower sound from the higher frequency harmonics. 
--found a link to this
http://en.wikipedia.org/wiki/Missing_fundamental

I read about this in regards to some dsp algorithm they were using to mimic lower frequencies in small systems like spherex that made things  sound deeper than they actually were being produced by the speaker,  by manipulating this effect with artificial modulations.

-Tony

Indeed, Petr Janata conducted an interesting experiment with a barn owl in which he played a song (‘The Blue Danube’) that had been completely stripped of fundamentals to the bird while monitoring its inferior colliculus. In fact, the firing of the owl’s inferior colliculus was fed to a speaker, which produced the missing fundamentals – pretty clear evidence that this is more than just a concept, but is the way brains work. It's also evidence for the fact that this 'filling in' happens rather early in auditory processing. Our brains, by the way, are masters at 'filling in' - typically, without our slightest awareness.

Of course, the other thing (as has been mentioned) about bass is that it is felt. That fact points up one of the shortcomings of the Fletcher Munson analysis – the testing was done using headphones.

---

For those interested in chasing down some of the research concerning the neurophysiology of missing fundamentals, here's a list: http://www.auditory.org/postings/1993/190.html

[*Scotty*]

I think JohnR has succinctly stated the truth of the matter, when the spectral relationships of the live performance have been captured by the recording, they are inevitably reproduced with these relationships intact by a system free of resonant behavior below the Schroeder frequency and possessing flat response from 20Hz to 20kHz.
 
Equal Loudness Contour Curves simply do not apply to the stereo system or its power requirements. They do apply when your listening levels are below 80phon and a loudness contour button would be useful for late night listening. I think there is a real place for this if it is implemented in the digital domain. This could be done quite precisely with a microphone located at the listening position and providing SPL information to the program for real time equalization of the bass frequencies. You wouldn't take the hit in transparency from the analogue circuitry this way and the correction could be much accurately applied.

 If you look at the Equal Loudness Contour Curves you will notice that they become compressed with decreasing frequency and are more than twice as close at 20Hz as they are at 1000Hz. This means that in fact we are more sensitive to relative SPL changes in the bass spectrum not less. A plus or minus 3db change in level below 40Hz can be perceived to be equivalent to as much as a 6dB change in SPL. It appears that you are much closer to the edge of the performance envelope in the bass spectrum and small changes in SPL levels at these frequencies can dramatically affect your impression of how good the system's bass performance is.
Scotty