Archived from groups: rec.audio.high-end (
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> >> I always thought the lower the frequencies the further it is heard.
> >> Am I wrong?
> >>
> >
> > This is true and is basic acoustic science. There is a tiny bit of
> > loss in the adiabatic movement of air as the sound wave propagates.
> > This is +/- proportional to the wavelength. You could loosely
> > summarize that for every cycle there is a certain amount of loss and
> > therefore because lower frequencies have longer wavelengths that they
> > will travel more distance per cycle and thus per unit energy loss. Off
> > hand I believe the attenuation curve is quadratic against a
> > logarithmic frequency scale. (if I'm wrong someone will reply)
> >
> > Your brain uses this principe, along with temporal left vs right
> > differences and reletive SPL differences, to tell you how far
> > something is away from you. In particular if something is pretty far
> > away then stereo preception will do you no good. You can hear this
> > phenominon all the time in music recordings.
> >
> > Of course wind can skew this a bit. Ever wondered why a busy road in
> > the area only makes lots of noise sometimes?
>
> Well, the most important factor is the decreasing sensitivity of our ears
> for lower levels of deep bass, which is a necessity to suppress the sound of
> our stepping feet on the ground.
> At 20Hz the 0db-loudness is at 70dB SPL, below this level we cannot hear
> anything any more, at 50Hz this threshold has gone down to 40dB SPL. If the
> SPL is above this value its perceived loudness rises much faster than higher
> frequencies. Look up "Fletcher-Manson" diagramm.
> The SPL is 6dB down by doubling the distance, only high frequencies get
> absorbed by the air, all bass frequencies are transported without loss, just
> the bigger surface will cause the decrease in level. Deep frequencies
> propagate equally into all directions.
Humm, that's indeed interesting to integrate Flechter-Munsen dynamics
into this discussion as well, en element which I hadn't thought about
combining with this issue. Yet in practice, I'm wondering how much it
is truly responsible for this phenomena in everyday life since you can
plainly hear the attenuation of higher frequencies in everyday life
situations which are usually well above threshold sensitive SPL
levels. Think about being a few hundred years from an outdoor rock
concert where the levels are still reasonbly loud and you hear mainly
low rumble. I guess you could summarize that when absolute SPL
thresholds start getting lower, that "perceived" high frequency
attenuation will increase to even a greater extent.