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. 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 <mailto:del at fandrichpiano.com%20> del at fandrichpiano.com — <mailto:ddfandrich at gmail.com> 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. -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://www.moypiano.com/ptg/pianotech.php/attachments/20110318/e7ca53db/attachment-0001.htm> -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: image/gif Size: 12657 bytes Desc: not available URL: <https://www.moypiano.com/ptg/pianotech.php/attachments/20110318/e7ca53db/attachment-0001.gif>
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