[pianotech] What is bloom,

[Bruce Browning]

Consider also phase changes!

On 19 March 2011 08:50, bergpiano <dan at bergpiano.com> wrote:

>  Del,
>
> It could be the waves returning to the player from the room. If the waves
> interact all kinds of things can happen. Each room will have it's character
> as well. Once those waves hit the air who knows what is happening.
> Refelective sound is very complex.
>
>
>  Dan Berg
> Berg Piano Services
> 407-884-1814
> http://bergpiano.com
> Your Home For Piano Help
>
> ----- Original Message -----
> *From:* Delwin D Fandrich <del at fandrichpiano.com>
> *To:* pianotech at ptg.org
> *Sent:* Friday, March 18, 2011 3:14 AM
> *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.
>
>


-- 
Bruce Browning
The Piano Tuner
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