Hi Jon,
Just across the pond from you, in the Department of Music, we've had
a fair bit of experience of this though not through rock concerts but
electroacoustic music ones. Now, unlike reportage recording/reproduction
systems where you're trying to recreate (or, at least, evoke) an original
acoustic event, electroacoustic concerts are 'stand alone' and are, in
themselves, an artistic event so messing with the bass isn't a problem.
What we found was that composers often had problems maintaining the
spectral balance of their pieces in the concert hall at least, compared to
what happened in the composition studio. For a performance on a loudspeaker
orchestra (check out 'BEAST" or the "Acousmonium") this would usually be
dealt with by the diffusion artist tweaking the spectrum (which s/he would
probably be doing, anyway, as part of the performance). But where you were
doing just replay ("tape music") whether Ambisonic or not, we wanted
something a bit more automatic. The problem, as we saw it, was the
compression of the perceived dynamic range at the low end of the Fletcher
Munson curves. The solution I came up with, at least for Ambisonics, was a
box of tricks which, initially anyway, processed just the W signal and sent
it to the sub. It consisted of a lowpass filter feeding a parallel
combination of a 2:1 compressor and a variable gain amplifier, the outputs
of which mixed together. The user had control of the filter frequency,
amplifier gain and compressor output level. Tweaking the controls gave a
greater or lesser degree of matching to an inverse F-M curve. This meant
that the lower frequency components could be made "linear" as far as the
listener was concerned. For some music, at least, this was of considerable
benefit. Of course, this didn't solve the problems of the directionality of
the bass but that's another story :-)
The box may still even be around somewhere in Music, but as I'm retired, I
don't actually - but, in any case, it's function has long since been
replaced by Max/MSP or Pd processing in the digital domain.
Dave
On 22 April 2015 at 21:25, jon burton <[email protected]> wrote:
> Thats interesting thanks Steve. I am looking for positives rather than
> negatives!
>
>
> Jon Burton
> Research Student MSc
> University of York.
> [email protected]
>
>
>
>
>
> > On 22 Apr 2015, at 21:21, Steven Boardman <[email protected]>
> wrote:
> >
> > Hi Jon
> >
> > I add more sub (from main mix) into the lfe channel for broadcast in
> Dolby
> > cinemas. For the same reasons. It doesn't register so much on A weighted
> or
> > Dolby leq (m) meters. This means one can use more headroom of the system
> > and push the dynamics and overall spl in the room. I know a few engineers
> > that do this for broadcast in cinemas.
> > Not sure of any research of the damaging effects though.
> >
> > Best
> >
> > Steve
> > On 22 Apr 2015 20:53, "jon burton" <[email protected] <mailto:
> [email protected]>> wrote:
> >
> >> There is a wealth of information regarding the negative effects of Low
> >> frequency noise but most of it relates either to vibration issues or
> sleep
> >> related problems. The low frequencies produced in concerts have had very
> >> little specific health related research. I recently had a long
> conversation
> >> with one of the major custom earplug manufacturers who was of the
> opinion
> >> that the low frequency levels were of little concern at rock and pop
> >> concerts and that is was the A weighted band that we should be concerned
> >> with. As I am looking at ways of reducing the A weighted levels by
> >> increasing energy in the sub 50Hz region I am looking for research done
> >> that may relate to this small but interesting area.
> >> I have over the past ten years been using sub to help produce a more
> >> immersive experience at low levels. I was wondering if any of the group
> had
> >> tried anything similar. I know there has been research done on gaming
> >> chairs using vibration but has anyone done work with sound waves?
> >>
> >> Thanks
> >>
> >>
> >> Jon Burton
> >> Research Student MSc
> >> University of York.
> >> [email protected]
> >>
> >>
> >>
> >>
> >>
> >>> On 22 Apr 2015, at 20:20, Jonathan Burton <[email protected]> wrote:
> >>>
> >>>
> >>>
> >>> On Wednesday, April 22, 2015, Peter Lennox <[email protected]
> >> <mailto:[email protected] <mailto:[email protected]>>> wrote:
> >>> I'd be interested in any references indicating deleterious effects on
> >> hearing of high amplitudes at LF, if anyone comes across any
> >>> cheers
> >>> ppl
> >>> Dr. Peter Lennox
> >>> Senior Fellow of the Higher Education Academy
> >>> Senior Lecturer in Perception
> >>> College of Arts
> >>> University of Derby
> >>>
> >>> Tel: 01332 593155
> >>> ________________________________________
> >>> From: Sursound [[email protected] <mailto:
> [email protected]> <javascript:;>] On Behalf
> >> Of Jörn Nettingsmeier [[email protected] <mailto:
> [email protected]> <javascript:;>]
> >>> Sent: 22 April 2015 19:20
> >>> To: [email protected] <mailto:[email protected]>
> <javascript:;>
> >>> Subject: Re: [Sursound] Infra sound & Sub bass.
> >>>
> >>> On 04/22/2015 06:49 PM, jon burton wrote:
> >>>> Hi I am new to the group but hoping someone may be able to help. I
> >>>> am looking at the positive effects of low frequencies in music,
> >>>> predominantly below 50Hz. This involves aural as well as
> >>>> mechanosensations. I am interested in seeing if reinforcing the low
> >>>> frequency content below 50Hz can help produce a more immersive
> >>>> listening experience at lower overall sound pressure levels
> >>>> (particularly when measured using the A weighting scale). Trouser
> >>>> flapping bass! I am struggling to find papers on the subject. Any
> >>>> suggestions are welcome!
> >>>
> >>> Well, it's not a secret that most live sound engineers, when faced with
> >>> a 99dB(A) rule, will mix into the A curve, i.e. crank up the bass a
> lot.
> >>> So there is plenty anecdotal evidence for more bass resulting in less
> >>> weighted sound pressure. For more perceived loudness, mixing in some
> >>> typical loudspeaker-like artificial distortion has prevented me from
> >>> getting beaten up at a "95 at the mixer" open air metal concert. Don't
> >>> ask me who came up with that rule, for that kind of music.
> >>>
> >>> But I've heard medical research hint at low frequency exposure having a
> >>> very damaging effect across the entire hearing spectrum, which means
> >>> that we are mixing around the rules but are actually endangering our
> >>> audiences.
> >>> Be sure to check the literature for this problem, to get a balanced
> view.
> >>>
> >>> --
> >>> Jörn Nettingsmeier
> >>> Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
> >>>
> >>> Meister für Veranstaltungstechnik (Bühne/Studio)
> >>> Tonmeister VDT
> >>>
> >>> http://stackingdwarves.net <http://stackingdwarves.net/> <
> http://stackingdwarves.net/ <http://stackingdwarves.net/>>
> >>>
> >>> _______________________________________________
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--
As of 1st October 2012, I have retired from the University.
These are my own views and may or may not be shared by the University
Dave Malham
Honorary Fellow, Department of Music
The University of York
York YO10 5DD
UK
'Ambisonics - Component Imaging for Audio'
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