[pianotech] What is bloom,

[Nicholas Gravagne]

Agreed. This is my take on it. However, the psychoacoustic idea (PI) is
considered bunk by some (they would have to argue with the likes of
Helmholtz and many physicists) owing to what seems to be a far too
open-ended and subjective realm. I can appreciate this point of view when
the PI is used carelessly to explain away or to explain "in" any pet theory
they may hold.

But clearly the amazing ear fills in the gaps and "smooth-curves" the choppy
effect of even listening to, say, A440. We don't hear this Hz as a staccato
effect of 440 acoustical pushes and pulls. That is to say, the ear will
analyze, filter and construct a useful resultant curve of many disparate
impulses.

On Fri, Mar 18, 2011 at 7:50 AM, David Love <davidlovepianos at comcast.net>wrote:

> I like the psychoacoustic explanation and it might well be a good one and
> relate to the actual shape or slope or rate of change of the sustain curve
> as well as the relationship between the chaos phase and the sustain phase.
> A sustain curve exhibiting a slower rate of change after the chaos period
> (or showing a relative flattening out) might be interpreted as a bloom when
> compared to a more rapid rate of decay.
>

Agreed. No extra energy required.


> Voicing could then be understood to influence bloom in terms of shaping the
> relationship between the chaos phase and the sustain phase.  It’s certainly
> a simpler explanation and those are generally more attractive, Occam’s
> Razor.
>

Ah, voicing. You once coined a phrase (at least for me): From Chaos to
Harmony.

>
>
> David Love
>
> www.davidlovepianos.com
>
>
>
> *From:* pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] *On
> Behalf Of *Delwin D Fandrich
> *Sent:* Friday, March 18, 2011 12:15 AM
>
> *To:* pianotech at ptg.org
> *Subject:* Re: [pianotech] What is bloom,
>
>
>
> Yes, well, I continue to wonder just what it is that we’re actually
> hearing. Below is an idealized illustration of what is happening at, and
> following, hammer impact. (It’s a little more idealized than I would like
> but I don’t have any of my own on this computer. This one is borrowed from
> the Five Lectures website.)The hammer strikes the strings at about 3 sec.
> There is a chaotic spike immediately following (the period of chaos is
> typically a bit wider than shown here). The sound immediately begins to
> decay at some fairly rapid rate but, for this note, at around 5 sec. the
> rate of decay changes.
>
> *[image: Description: Description: Fig 1. Typical decay of a piano tone as
> illustrated by the sound pressure level versus time (Eb3 = 311 Hz). The
> decay process is divided into two parts; an initial attack part with a fast
> decay (prompt sound) followed by a sustained part with slow decay
> (aftersound).]*
>
> From what I’ve been able to figure out, the knee (at around 5 or 6 sec.) is
> where the strings vibration pattern changes from a predominately transverse
> motion (perpendicular to the bridge) to a more random, or rotational
> pattern. The note is still dying out but at a slower rate. It continues thus
> until the sound dies out or, as in this illustration, the damper drops.
>
> In all the samples I’ve recorded and studied over the years I’ve never seen
> the sound level increase after hammer impact and that first chaotic wave
> pattern. They all end up looking like some variation of this. More ragged
> and uneven sometimes but they follow this generally pattern.
>
> It leaves me wondering if what we think we hear as “bloom” isn’t at least
> partially—perhaps predominately—psychoacoustic. Our ears—or our brain’s
> interpretation of what our ears detect—quickly become accustomed to that
> rapid drop-off following the chaotic hammer impact and, when the waveform
> gets to the knee and the decay rate slows (sometimes dramatically) we
> interpret the change as “bloom.”
>
>
>
> ddf
>
> Delwin D Fandrich
>
> Piano Design & Fabrication
>
> 6939 Foothill Court SW, Olympia, Washington 98512 USA
>
> Phone  360.736.7563 — Cell  360.388.6525
>
> del at fandrichpiano.com <del at fandrichpiano.com%20>— ddfandrich at gmail.com
>
>
>
> *From:* pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] *On
> Behalf Of *Dale Erwin
> *Sent:* Thursday, March 17, 2011 5:20 PM
> *To:* pianotech at ptg.org
> *Subject:* Re: [pianotech] What is bloom,
>
>
>
> Del
>   Understood. I can't measure it empirically either. Fortunately we can
> hear it.
>



-- 
Nick Gravagne, RPT
AST Mechanical Engineering
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