Downloads & Miscellanea
- Red bass drum
Shaped tone bursts are used to check maximum levels for individual frequency bands; they are also useful for evalutaion distortion performance and even polarity checking. Siegfried Linkwitz (yes, the same Linkwitz that goes with Riley) started using these pulses in the early 80s. Don Keele later refined the concept by defining the window that made the pulses be almost exactly one third-octave wide in frequency as well as developing composite bursts made up of bass frequency pulses. Tomlinson Holman (as in THX) would also advocate the use of tone bursts and incorporated them into his test disks for the Hollywood industry coining the term "boink tests".
My contribution here takes the form of what I call "9-yard shaped tone bursts", a combination of third-octave band pulses spanning the complete audio spectrum and added together in a controlled way such that different shades or "colors" can be achieved such as white, pink or red (brownian). The illustration shows 131072-point FFT spectra of some of these full-range composite sinewave pulses in pink, red and EIA-426B (shown in yellow) "colours". Additionally, the "red bass drum" limits the "red" burst spectrum to 40 Hz on the low frequencies.
Of these 9-yard bursts, the "red bass drum" (in Spanish, bombo rojo) can be downloaded from here. For lightness,
15K
, this 16 bit 44.1kHz wave file has been compressed into a ZIP archive. The file has been padded with silence up 5 seconds, for sensible looping. It is a kind of laboratory (yet highly musical) bass drum (except that it does not have harmonics as such, but all frequencies from 40 to 20k Hz, just like noise would), with a "red" spectrum; we think this is a great signal for an instant all-round loudsèaker system check (play either left or right channel only).
 (Red bass drum sound licensed under this Creative Commons License)
- Whalebone & Idling spaceship
While making some test sounds i wondered what a large bunch of
logarithmically spaced tones spanning the audible band would sound
like. As a synthesist, i have always enjoyed designing highly
modulated sound textures using a music synthesizer. However, i never
thought mathematically generated steady-state sounds could provide
much liveliness, but here are whalebone and idling spaceship to prove me wrong.
They are like the picket fence sound (same thing with one tone per 1/3rd
octave band) on steroids.
Using the same 1/24th octave resolution
i often use for measurements, you get a highly modulated sound that i (following the picket
fence analogy on an insired moment) named whale bone, since a whale's
baleen (also referred to as "whale bone") is made up of an average of 260 plates,
which happens to be extremely close to the 248 frequencies i use to
cover the 1/3 octave bands from 20 to 20k Hz at 8 tones per 1/3rd
octave bands, i.e. 24 tones per octave).
The sound can be downloaded from here. For lightness,215K,
it is presented in mono, using 8 bits and with a
sampling frequency of 22 050 Hz (so there are tones to 11 kHz only).
Along the same route we find idling spaceship. Here we increase the tone density and generate around 2000 tones up to 20 kHz. The result is a sound that develops over time and can be downloaded from here (646K, also 8-bit/22k Hz).
Those last two are probably useless "pink" coloured sounds, but I thought they were amusing.
 (The two wave files above are licensed under this Creative Commons License)
- Piston animations
The animation below shows the directivity for a cone loudspeaker which has been simulated as a piston. The resulting radiation patterns come from Bessel functions, and can be seen to beam as frequency increases
The animation below also shows the directivity for a cone loudspeaker which has been simulated as a piston, but is represented as 3D directivity balloons.
Lobing is more clearly visible since a dB representation is used.
- Articles
The following online
versions of some of my articles can be found on the web:
- Loudspeaker directivity, published by Sound and Video Contractor magazine (USA) in
April 1999.
The online version only contains partial text and does not include
the numerous illustrations, but an updated version can be found here. PDF
en español (original spartan PDF in Spanish)
- The Power Alley published
by Live
Sound and LiveAudio.com / ProSoundweb.com in 2003. Ignore the
Sound and Video Contractor version if you ever see it, as it
contains nonsense the editor added. Left-right
subwoofer interactions being inevitable and very apparent in
outdoor applications, this one became a popular piece. Though the
explanation for the power alley is far from being rocket science, this became a very popular piece, since for some reason
nobody had actually sat down to extensively describe an effect that can be easily felt outdoors, probably partly because back subwoofer modelling was not available at the time (I had to use dimensional analysis and some custom speaker directivity and wireframe files). PDF
en español (original spartan PDF in Spanish)
- Electronic Versus Physical: An Analysis Of Shaping Array Directivity published
by Live
Sound and ProSoundweb.com in 2011. It explains why steering or arcing an array yields completely different results when done electronically (using delay) and physically. Case studies are provided to illustrate caveats for each depending on the application
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