[xnor]

Quote:

Yes, there is no question that these frequencies are normally inaudible, but the articles linked to suggest that they still affect us. Who knows if there is any effect at the typical small and/or attenuated levels in most recorded music. Do you know where the high pass filter is usually set in the mixing/mastering process?
 
I have owned amplifiers in the past that had switchable high pass filters to prevent any extreme low frequencies causing problems in the speakers.

Vocals up to roughly 100 Hz, guitar about 150 Hz, bass and kick drum up to about 40 Hz.

 

[Nirmalanow]

Quote:

Vocals up to roughly 100 Hz, guitar about 150 Hz, bass and kick drum up to about 40 Hz.

Why would an engineer filter out frequencies below 150hz on guitar music when the first 3 strings are tuned lower than that?

 

[jaddie]

Quote:

Why would an engineer filter out frequencies below 150hz on guitar music when the first 3 strings are tuned lower than that?

Who said they do?

 

[xnor]

Quote:

Why would an engineer filter out frequencies below 150hz on guitar music when the first 3 strings are tuned lower than that?

These are just rough upper limits. Usually, you will back down a bit if you notice that the instrument/voice starts sounding anemic.
 
It can also be an artistic choice but usually it's used to clean up the low end.

 

[jaddie]

Mastering and recording engineers DO NOT categorically cut off low frequencies, not for guitars, vocals or any other instruments.  There are occasions where the recording environment may have sub-sonic noise that must be reduced, like recording an orchestra in a hall with a subway train running below, but the filtering involved is situation specific.  
 
Location sound recording for film often dictates low frequency cut, and it's often applied during the recording to prevent low frequency overload of the recoding system.  In that case, a cut below 150Hz is not uncommon, but again, it's situational.  And often just not done.  A good example would be in episodic TV and sitcoms.  I've heard subsonic noise come and go, shot by shot, in 30 Rock, which is largely shot on a soundstage.  My subwoofer reproduces it faithfully, its distracting, and should have been cut off in post, but they clearly didn't mix on a system with extended bass, so they missed it.
 
The reasons for low frequency cut fall into the categories of noise control or artistic choice, but noise control is the most likely.   The goal is to remove the offending noise as much as possible without touching the desired signal, and its done with state-variable filters that can be custom tuned both in cut frequency and roll-off slope.  There are also active noise reduction methods, both analog and DSP based, which can be tuned to isolate the noise without damage to the desired signal.
 
Excessive sub-sonic noise can cause problems in playback.  For example, sub-sonic record rumble (vinyl) can cause woofer cones to wiggle enough that they induce a doppler frequency shift in mid band frequencies.  Rolling off record rumble below 20Hz solves the problem. 

 

[Nirmalanow]

Quote:

Mastering and recording engineers DO NOT categorically cut off low frequencies, not for guitars, vocals or any other instruments.  There are occasions where the recording environment may have sub-sonic noise that must be reduced, like recording an orchestra in a hall with a subway train running below, but the filtering involved is situation specific.  
 
Location sound recording for film often dictates low frequency cut, and it's often applied during the recording to prevent low frequency overload of the recoding system.  In that case, a cut below 150Hz is not uncommon, but again, it's situational.  And often just not done.  A good example would be in episodic TV and sitcoms.  I've heard subsonic noise come and go, shot by shot, in 30 Rock, which is largely shot on a soundstage.  My subwoofer reproduces it faithfully, its distracting, and should have been cut off in post, but they clearly didn't mix on a system with extended bass, so they missed it.
 
The reasons for low frequency cut fall into the categories of noise control or artistic choice, but noise control is the most likely.   The goal is to remove the offending noise as much as possible without touching the desired signal, and its done with state-variable filters that can be custom tuned both in cut frequency and roll-off slope.  There are also active noise reduction methods, both analog and DSP based, which can be tuned to isolate the noise without damage to the desired signal.
 
Excessive sub-sonic noise can cause problems in playback.  For example, sub-sonic record rumble (vinyl) can cause woofer cones to wiggle enough that they induce a doppler frequency shift in mid band frequencies.  Rolling off record rumble below 20Hz solves the problem. 

That all makes sense. And your mention of how vinyl can create a rumble probably explains why years ago, my receivers often had a switchable low frequency filter to prevent the problem.

 

[xnor]

Quote:

Mastering and recording engineers DO NOT categorically cut off low frequencies, not for guitars, vocals or any other instruments.

It depends. In some genres this is quite common to be able to better maximize volume (in other words squish dynamic range, see loudness war).

 

[jaddie]

Quote:

It depends. In some genres this is quite common to be able to better maximize volume (in other words squish dynamic range, see loudness war).

Actually, loudness processing is nearly all about reducing crest factor (peak to average ratio), and not constricting frequency response.  In fact, several loudness processor tools us a multi-band processing technique to permit higher degrees of processing without as much audible artifact.  The bottom band of a 3 or 4 band processor is centered at 150Hz.  Loud and dense bass is actually key to a loud sounding recording.  They would only band limit sub-sonics below 20Hz, and yes, that's done routinely.  A multi-band processor will increase spectral density over the entire band, and will act as a dynamic graphic equalizer as its slow average or RMS portion, then act as a band-specific peak limiter, followed by a full bandwidth fast peak limiter, then clipper.  But there's no intentional rolling off below 150Hz, 20Hz and below only.

 

[xnor]

Doesn't change what I said and it's not about constricting frequency response but removing energy of stuff that is more or less in the background or masked anyway. This is also done way before any compression.

 

[jaddie]

Quote:

Doesn't change what I said and it's not about constricting frequency response but removing energy of stuff that is more or less in the background or masked anyway. This is also done way before any compression.

Yes, right, we are in agreement.  We just vary a bit on what we define as the energy to be removed, though I certainly agree with what you just said.  And I'm sure we agree that it's never just as simple as a corner frequency of a high pass filter that is always used, like 150Hz.  Yes, best done before compression.

 

[Nirmalanow]

It seems that hypersonic sounds may affect us more than we realize also: http://jn.physiology.org/content/83/6/3548.full

 

[nick_charles]

Quote:

It seems that hypersonic sounds may affect us more than we realize also: http://jn.physiology.org/content/83/6/3548.full

 
The Oohashi paper has been discussed extensively here and elsewhere. To date nobody has been able to replicate the results (Ashihara and fellow NHK colleagues tried) and peer researchers have suggested the effect possibly being related to IMD rather than ultrasonics per se. Oohashi's work relates to physiological responses but never suggests that listeners can consciously differentiate between full spectrum and bandwidth limited sound.

 

[Nirmalanow]

Quote:

 
The Oohashi paper has been discussed extensively here and elsewhere. To date nobody has been able to replicate the results (Ashihara and fellow NHK colleagues tried) and peer researchers have suggested the effect possibly being related to IMD rather than ultrasonics per se. Oohashi's work relates to physiological responses but never suggests that listeners can consciously differentiate between full spectrum and bandwidth limited sound.

Thanks for the info. I was getting pretty far off the original topic anyways which is about an audible difference with a boosted low bass even in music which has little or no notes in that frequency range.

 

[ab initio]

Here's an interesting wiki article on implied fundamentals and how the ear (actually, more likely the brain) can be tricked into thinking a sound is lower than it really is. It also points out a few scenarios where music would be intentionally mastered with the lowest frequencies filtered out and harmonics added to suggests that the low end was still there. It seems to be done most frequently with "pop" music that will be consumed by masses with low quality sound systems.
 
The article brings up the recent remake of Lady Marmalade and how it was specifically engineered with implied fundamentals for the low-end and I actually intentionally watched the YouTube video to check it out (first time I've actually tried to listed to the work by any of the song's collaborators) and indeed, the effect is quite obvious once you know to listen for it. The song is actually mixed to sound like it's playing on crappy speakers with lacking low end!
 

 
Anyway, I came across this and it reminded me of the discussion in here. Also, reminded me of the scope readings from my guitar amplifier using an overdrive setting and the bass tone knob turned down (to keep the neighbors downstairs happy---otherwise i'm all for 11 on everything )
 
Cheers!
 

 

[xnor]

Another prime example of the brain messing with what's really there.