G8MNY TECH 25.08.19 04:33l 153 Lines 6816 Bytes #365 (0) @ WW
BID : 18856_GB7CIP
Subj: AF Noise Generator
Path: OK0NBR IR2UBX DB0RES DB0OVN DB0GOS ON0AR GB7CIP
Sent: 190825/0729Z @:GB7CIP.#32.GBR.EURO #:18856 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW

By G8MNY (New Nov 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
This is a audio noise generator that can make:-

WHITE NOISE that has constant energy per Hz.

PINK NOISE that has constant energy per octave, with a series of CRs to give
a 3dB per octave filtered white noise.
RED NOISE that has reducing noise per octave, with a single CR for 6dB per
octave filtering of the white noise.

SCHEME
White ┌──────────┐White
┌───┐ ┌───────┐Noise┌──┤Attenuator├──o
│Osc├─┤Pseudo ├─────┤ └──────────┘ ┌──────────┐
└───┘ │Random │ │ ┌────────────┐ ──┤Buffer Amp├─ Output
│Counter│ ├─┤Pink Filters├─o └──────────┘
└───────┘ │ └────────────┘
│ ┌─────────┐ Red
└──┤CR Filter├───o
└─────────┘

PSEUDO RANDOM NOISE GENERATOR
┌─────────────────────┐ ____
│ ┌─────────────────┐ │ + ──┬─┤7808├─┬──+12V
│ │ 4006 #4│ │#8 ===└──┬─┘===
│ │ ┌─────────────┐ │ │ 10u└────┼───┘10u
│ └─┤4 D2 D1+4 13├─┘ │ _│_
Start Pulse └───┤6 D4 D2+4 11├───┘
+ ──┤├───┬──┤ ├───┬──────┤1 D1 │
+10u 27k 27k ┌───┤3 CLK D3+4 10├───┐#17
_│_ │ │ ┌─┤5 D3 D4+5 9├─┐ │
│ │ │ └─────────────┘ │ │
│ │ │ 1st counter #13│ │
│ │ └─────────────────┤ │
│ │ __ │ │
4030 Gates │ │ #34113 / 1│├──┘ │
__ └──)───────────(3 (( │
__ + ┤│6 \ │ \ 2│├────)─────────┐
+ ┤│8 \ )) 4)──┤ ~~ │ │
)) 10)─┬──┤│5 / │ ┌───────────────────┘ #26 │
┌─┤│9 / │ ~~ │ │ ┌─────────────────────────┐ │#34
│ ~~ └┤├─┬─20k──┤ │ │ ┌─────────────────────┐ │ │
│ n18 │ │ │ │ │ ┌─────────────────┐ │ │ │
│ __ │ │ │ │ │ │ 4006 #21│ │ │ │
│ /13│├ + │ │ │ │ │ │ ┌─────────────┐ │ │ │ │
└─(11 (( │ │ │ │ │ └─┤4 D2 D1+4 13├─┘ │ │ │
\12│├─10k─┘ │ │ │ └───┤5 D3 D4+4 8├───┘ │ │
~~ │ │ └─────┤6 D4 D2+5 12├─────┘ │ DIGITAL
113kHz Osc │ └───────┤1 D1 D3+4 10├───────┴─ WHITE NOISE
├─────────┤3 CLK │ 3Hz-56kHz
83p === └─────────────┘
_│_ 2nd Counter

After a count of #34113 the pseudo random noise code repeats.

AF FILTERS
┌──────┬── +12V
NOISE ┬───────────56k───┬───────┐ 220k │
│ 2k7 │White │ 741 │
│ _│_ │ u33 │ │\│7
│ └o ──┤├──┼────┤2 \ 25u
├─6k8──┬────┬───┬──────┬───oPink │ │± 6 ───┬─┤├─┬─1k─(o Output
│ 1u│ u27│ │ 33n│ ┌o │ ┌─┤3 / │+ │ │
│ === === ===2x === │Red 220k │ │/│4 │ │ │
│ │ │ │47n │ │ │ ├───)──10k┘ 100k │
│ 3k 910 270 │ │ │ 2k7 │ │ │
│ ├────┴───┴──────┘ │ │ │+ │ │ │
│ _│_ │ │ === │ │ │
│ │ └──┴───┴──────────┴────┤
└───────────56k───────────┤ 470u _│_
u1 === BUFFER AMP
_│_

SPECTRUMS
Level Constant Analyser Bandwidth
+0dB┤------------------------------------------------------------------White
-3dB┤ \'─._ Noise
-6dB┤ \ '─-..__
-9dB┤ \ ''─-...____ Pink Noise -3dB/O
-12dB┤ '─. ''''────-----......______
-15dB┤ Red ~─._ '''''''──────----- -18dB┤ Noise ''─-..
-21dB┤ -6dB/O '''─-...
-24dB┤ '''──--....___
-27dB┤ ''''──---...___
-30dB┤ L I N E A R S C A L E '''────----
├───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬──┬───┬ Freq
0 200 400 600 800 1k 1k2 1k4 1k6 1k8 2k 2k2 2k4 2k6 2k8 3k 3k2 3k4 Hz

Level
+0dB┤-------------------------------------------White
-3dB┤ \'-._ Constant Analyser Bandwidth Noise
-6dB┤ \ '-._
-9dB┤ \ '-._
-12dB┤ \ '-._Pink
-15dB┤ Red \ '-._Noise
-18dB┤ Noise \ '-._-3dB/O
-21dB┤ -6dB/O \ '-._
-24dB┤ \ '-._
-27dB┤ \ '-._
-30dB┤ \ '─._
-33dB┤ L O G S C A L E \ '-
└┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬─ Freq
16 32 64 125 250 500 1k 2k 4k 8k 16k 32k Hz

Level
+15dB┤ '─._ _.─'
+12dB┤ Red '─._ Constant Q Analyser _.─'
+9dB┤ Noise '─._ Filters _.─' White
+6dB┤ '─._ _.─' Noise
+3dB┤ '─._ _.─'
0dB┤-----------------------*---------------------Pink
-3dB┤ _.─' '-._ Noise
-6dB┤ White _.─' '─._ Red
-9dB┤ Noise _.─' '─._ Noise
-12dB┤ _.─' '─._
-15dB┤ _.-─' L O G S C A L E '─._
└┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬─ Freq
16 32 64 125 250 500 1k 2k 4k 8k 16k 32k Hz

With constant Q filters in an AF spectrum analyser display the pink noise
gives a flat response.

Level
0dB┤ .──────────────────────────────────────.
-1dB┤.·' '·.
│ L O G S C A L E
└┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬─ Freq
16 32 64 125 250 500 1k 2k 4k 8k 16k 32k Hz

With Magnetic systems like tape, magnetic cutting heads, etc. Red noise will produce a flat spectrum, with constant bandwidth analyser.

SOUND COLOURATION
With good hearing it is possible to judge AF response of system especially
when comparing using just these noises.

The White noise lets you predominately hear the top end, as the ear is like a constant Q analyser. The Pink noise lets you judge the whole range, while the Red noise lets you more easily concentrate on the bass resonances.

Used with a good graphic equaliser, mainly of the system colourations
(LS + room etc.) can be mostly ironed out.


Why Don't U send an interesting bul?

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