<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style></style></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1>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. <o:p></o:p><img width=301 height=223 id="Picture_x0020_4" src="cid:image001.gif@01CBE500.EADEECF0" alt="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)."><o:p></o:p>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.<o:p></o:p>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. <o:p></o:p>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.”<o:p></o:p><o:p> </o:p>ddf<o:p></o:p>Delwin D Fandrich<o:p></o:p>Piano Design & Fabrication<o:p></o:p>6939 Foothill Court SW, Olympia, Washington 98512 USA<o:p></o:p>Phone  360.736.7563 — Cell 360.388.6525<o:p></o:p><a href="mailto:del@fandrichpiano.com%20">del@fandrichpiano.com </a>— <a href="mailto:ddfandrich@gmail.com">ddfandrich@gmail.com</a><o:p></o:p><o:p> </o:p>From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of Dale Erwin Sent: Thursday, March 17, 2011 5:20 PM To: pianotech@ptg.org Subject: Re: [pianotech] What is bloom,<o:p></o:p><o:p> </o:p>Del   Understood. I can't measure it empirically either. Fortunately we can hear it.<o:p></o:p></div></body></html>