[sdiy] Harmonic bandwidth

[Scott Gravenhorst]

Tom Wiltshire <tom at electricdruid.net> wrote:
>
>On 8 Jan 2008, at 16:09, Tim Daugard wrote:
>
>>> There is one source of possible differences between the waveforms,
>>> which is that they've all been normalized to their maximum level.
>>> Given that the waveshapes won't have the same maximum peak level,
>>> this is likely to produce minor level differences between them.
>>>
>>> However, they've all got exactly the same 20 harmonics in exactly the
>>> same proportions.
>>
>> Measured with?
>
>Not measured, generated. The samples have been created artificially  
>from a script and then saved as AIFF files. The script simply adds  
>together 20 harmonics in the required amounts for a ramp wave ( 1,  
>1/2, 1/3, etc). Thus the generated sound is as accurate as the  
>floating-point internal maths and the 16-bit AIFF output. They  
>definitely do have the same proportions of each harmonic.
>
>The only possible source of error is the normalization of the result  
>to the full 16-bit range. I could remove that too, if anyone _really_  
>thinks it affects the experiment.
>
>> You would probably have to measure the frequency of each harmonic  
>> within a
>> few hertz and the amplitudes within 1db or less. I was surprised,  
>> after many years as
>> being a technician, how little the change was required to make a  
>> huge difference in sound.
>> No magic wire theories, but there are changes that fall in the  
>> tolerance ranges of test
>> equipment that can be heard by the ear. It's amazing what the ear  
>> and brain can interpret
>> (and misinterpret).
>
>I think the key there is 'misinterpret'. There's lots of evidence  
>that people hear differences where they think there are some - like  
>when they plug in their super-duper audiophile hifi using a new  
>platinum-plated mains cable.The improvement is subtle, but  
>_definitely_ there, ask anyone who just paid $400 for a mains cable! ;)

Yes, a sort of placebo effect.  I guess we're back to using a soundproof anechoic
chambre with high end equipment and do blind A/B tests with many individuals.  But
hasn't this already been done?  I'd love to see the result data of that.

-- ScottG

-------------------------------------------------------------

-- Scott Gravenhorst
-- GateMan-III - FPGA Based Monophonic MIDI Synthesizer with SVF
-- PolyDaWG/8 - FPGA Based 8 Voice Polyphonic MIDI Synthesizer
-- FatMan: home1.gte.net/res0658s/fatman/
-- NonFatMan: home1.gte.net/res0658s/electronics/
-- When the going gets tough, the tough use the command line.