[pianotech] What is bloom,

[bergpiano]

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 
  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. 



  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 — 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.
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