[pianotech] What is bloom,

[David Love]

Here's another way to look at it. The amount of potential energy in the system is represented by the sum of the compression in the soundboard system (as Nick describes) plus the amount that can be delivered by the hammer, much like a wrecking ball at the peak of its arc poised to crash into the building. Different systems may have those two sources in different proportion. For the same energy output you might have one system that relies on a greater amount stored in the soundboard and one that relies on a greater amount delivered from the hammer. The differences in the way the energy is released by virtue of that proportional difference  and how that manifests itself acoustically might go some way toward  answering the JD question and the notion of "bloom", whatever that is . With more energy stored in the board the total system relies less on hammer input and the same  total release of energy can be  achieved with less energy coming from the hammer. When you think about the differences between that Steinway we loved with very light and soft hammers that seems to come alive at the slightest touch and the Yamaha that requires some greater input of energy it all seems to fall into place.

David Love
www.davidlovepianos.com
(sent from bb)

-----Original Message-----
From: Nicholas Gravagne <ngravagne at gmail.com>
Sender: pianotech-bounces at ptg.org
Date: Fri, 18 Mar 2011 08:36:53 
To: <pianotech at ptg.org>
Reply-To: pianotech at ptg.org
Subject: Re: [pianotech] What is bloom,

I think so. This has to be the heart and soul of the whole matter. Voicing,
then, evens things out and brings out the best balance, but the choice of
hammers is important, after which the voicer can only work with the
foundation offered by the belly.

Potential energy (PE) is achieved, and is proportional to, the measurable
compression of the soundboard assembly under the force of downbearing. We
already know that a string is useless until it is stretched to a high
tension; PE is introduced and ready to be tapped. Likewise, hammer felt
stretched and compressed over a molding contains PE, also ready to be
tapped. PE becomes Kinetic Energy (KE) when tapped, or set in motion. The
more PE stored, the more KE is available.

Clearly, too much of good thing spoils the effect. There are limits and
points of diminishing returns.

On Fri, Mar 18, 2011 at 7:59 AM, David Love <davidlovepianos at comcast.net>wrote:

> Meant to add here, if that’s true, then what exactly impacts the shape of
> that curve?  I still like the idea of how much potential energy is stored in
> the system and the relationship between the tension of the two springs
> (string and soundboard).
>
>
>
> David Love
>
> www.davidlovepianos.com
>
>
>
> *From:* pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] *On
> Behalf Of *David Love
> *Sent:* Friday, March 18, 2011 7:51 AM
>
> *To:* pianotech at ptg.org
> *Subject:* Re: [pianotech] What is bloom,
>
>
>
> 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.  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.
>
>
>
> 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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