[PD] making puredata headphone-safe

[Hans-Christoph Steiner]

On Aug 31, 2011, at 8:09 AM, Roman Haefeli wrote:

> On Mon, 2011-08-29 at 12:19 -0400, Martin Peach wrote:
>> On 2011-08-29 11:52, Hans-Christoph Steiner wrote:
>>>
>>> On Aug 23, 2011, at 3:43 PM, Martin wrote:
>>>
>>>> On 23/08/11 03:29 PM, Stephen Lavelle wrote:
>>>>> I've managed to hurt my ears twice over the past two days when  
>>>>> using
>>>>> PD w/ headphones. Even at lowest system volumes, it seems that
>>>>> Terrible Things can happen. Are there any precautions that I can  
>>>>> take
>>>>> to make it feel less like I'm taking my life into my hands when I
>>>>> have to use headphones?
>>>>>
>>>>>
>>>>>
>>>>
>>>> Try making a [noise~] connected directly to a [dac~] and set the
>>>> headphone volume so you can live with that. Nothing will ever be
>>>> louder than that.
>>>
>>>
>>> Hmm, I don't think that's actually true in all cases. On a MacBook  
>>> Pro
>>> running Mac OS X, I've had the volume set to one above mute, but had
>>> massive feedback from LPC patches that were very very loud. [noise~]
>>> would be very comfortable at that volume setting. I think some  
>>> platforms
>>> do the output mixing in the digital domain, so my min volume would  
>>> be
>>> [*~ 0.01], so that this would still make a very loud sound:
>>>
>>> [noise~]
>>> |
>>> [*~ 999999]
>>> |
>>> [*~ 0.01] (i.e. the Apple output mixing)
>>> |
>>>
>>> In this particular case, the sound output actually gets shutdown
>>> entirely, so you have to reboot to get sound output again.
>>>
>>
>> That make no sense. How can you have two sounds at the same level  
>> going
>> into a mixer that come out at different levels? Or do you mean that a
>> squealing sound is perceived to be louder than white noise? Maybe you
>> could demonstrate with a patch?
>>
>
> I always had the feeling, that on OS X on MacBooks (Pro) the sound
> coming from the speakers is heavily processed. Audio sounds a lot
> 'punchier' than for example the same audio played on the same machine
> from Linux. I haven't had a chance to play around with it, since I  
> don't
> own a MacBook, but from what Hans says, to me it sounds as the
> application output is not clipped to -1/1 before going to the  
> (CoreAudio
> internal?) dynamics stage, but processed and limited first and only  
> then
> sent to the speakers. This would also explain, why the setup Hans
> explained above would completely shutdown the sound output.  Probably,
> if you wait long enough, sound would come back again, assuming that  
> it's
> the limiter's release time, that becomes very long due to the very  
> high
> level coming in...
>

Yes, CoreAudio does do processing on the audio before outputting it.   
I forget all the details.

.hc

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