Does SRBOX/Microphone setup effect RTs?

Tue Aug 5 18:09:37 UTC 2014

Thank you both for your responses and input. I am leaning more towards 
using two microphones for simplicity.  Maybe in the future I will revisit 
this issue and try to come up with something.

Thanks,

David 

On Friday, August 1, 2014 2:46:05 AM UTC-5, Michiel Sovijärvi-Spapé wrote:

> Hi, 
> Wouldn't the use of two (perhaps even taped together) microphones make a 
> lot 
> more sense? Given that these do very different things: record onset of 
> audio 
> vs record audio, I can think of few reasons why these would need to be 
> very 
> exactly synchronised - apart from that warm feeling we all get from hyper 
> precise timing, obviously! Anyway, the benefit would be that the audio 
> microphone can then be a very good, studio quality, microphone, rather 
> than 
> the SRBox voicekey one which I don't think was really built for audio 
> analysis. Second, it makes from an audio engineer's point of view some 
> sense 
> to direct microphone's different (e.g. a little underneath the mouth). 
> Third, you could use the onset of the SRBox voicekey as a trigger to start 
> an audio input object. Finally: you could always try to sync the data 
> offline if you send out a tone (e.g. at >20 Khz) at the onset of your 
> critical stimulus, then write a bit* of matlab code to calculate the 
> distance between beeps and first human vocal range (0.5<KHz<4), and save 
> the 
> chunk as data - it has certain benefits, since you will be more sure that 
> it's not just some subject's sigh that triggers the voicekey. 
> Anyway, just some ideas, maybe one helps. 
> Best, 
> Michiel 
>
> * That sounds like it's little work - obviously, it's not, but maybe there 
> are toolboxes out there already. 
> PS: Many audio interfaces (cards) do provide line level inputs, I've 
> previously recommended M-Audio Fast Track USB before as a cheap one (also 
> comes with dedicated ASIO drivers and such which might help E-Prime 2 
> audio 
> out latency) 
> ------------ 
>
> Dr. Michiel Spapé 
> Helsinki Institute for Information Technology HIIT 
> Aalto University & University of Helsinki 
> Finland 
>
>
> -----Original Message----- 
> From: e-p... at googlegroups.com <javascript:> [mailto:
> e-p... at googlegroups.com <javascript:>] On Behalf 
> Of David McFarlane 
> Sent: 31 July 2014 18:58 
> To: e-p... at googlegroups.com <javascript:> 
> Subject: Re: Does SRBOX/Microphone setup effect RTs? 
>
> David, 
>
> I dearly hope that you get simultaneous voice key and sound recording to 
> work with a single microphone, and then report back here on how to do it. 
>  I 
> never got that to work here, we gave up and used two microphones, one for 
> the voice key (SRBox) and one for sound recording through the computer's 
> mic 
> input.  Some details ... 
>
> In short, when we used any sort of Y splitter to connect one mic to both 
> SRBox and cmoputer mic input, we had trouble getting the voice key to 
> respond, and the recorded sound contained a high-pitched whine.  I worked 
> on 
> this with PST Support, and they could not do much better themselves -- in 
> their own tests using a splitter, either the voice key did not work, or 
> the 
> audio quality was degraded (e.g., low volume). 
>
> In case it helps, the SRBox uses a dynamic microphone (see 
> http://en.wikipedia.org/wiki/Microphone ), with a 3.5mm unbalanced TS 
> (tip-sleeve) connector.  Computer mic inputs typically use a condenser 
> mic, 
> with a 3.5mm TRS (tip-ring-sleeve) connector where the computer may supply 
> power to the mic through the ring.  So things get complicated already 
> right 
> there.  Beyond that, I suspect that each device connected to the 
> microphone 
> presents an additional load, and the microphone simply cannot handle the 
> load of two input devices, which would account for the loss in volume. 
>
> What we need, of course, is a device that presents a low load to the 
> microphone, and can drive multiple loads for the next stage.  Ordinarily, 
> that device would be a preamp that supplies line-level signals to the next 
> stage.  Unfortunately, in our case a line-level signal will likely 
> overload 
> our inputs -- the SRBox can take only a mic-level signal, and many 
> computer 
> sound devices no longer provide a line-level input, they provide mic-level 
> input only.  If you can find a device that takes a mic-level input and 
> then 
> buffers that to provide output to multiple mic-level inputs, that would be 
> great, but I asked around and could not find such a device.  One other 
> option might be to use a preamp, as mentioned above, and then attentuate 
> the 
> preamp output using something like a series resistor to the mic-level 
> inputs.  I have not yet tried this myself, so if you get this to work 
> please 
> write back.  (Even if this works, it just seems twisted -- I mean, first 
> we 
> would boost the signal from the mic, then attenuate the boosted signal 
> back 
> down to mic level so that we could feed it into another mic input that 
> then 
> boosts it yet again -- sheesh!) 
>
> So in sum, splitting a microphone between the SRBox voice key and the 
> computer sound card is not as straightforwared as you might think, and in 
> the end using two microphones still seems the best solution. 
>
> But to answer your question, I cannot think of any reason that using a 
> splitter would affect the measured reaction time, the electric signal 
> should 
> travel at the same rate with or without a splitter.  Of course, that 
> should 
> be tested empirically (and no one should just take my work for any of this 
> :) ), but I would be very surprised if it made any difference.  But note 
> that, even with a splitter, as a result of latencies in sound recording 
> you 
> will almost certainly find a discrepancy between RT measured by voice key 
> vs. sound recording, see thread at 
> https://groups.google.com/d/topic/e-prime/DcKdgNJKAlM . 
>
> ----- 
> David McFarlane 
> E-Prime training 
> online:  http://psychology.msu.edu/Workshops_Courses/eprime.aspx 
> Twitter:  @EPrimeMaster (https://twitter.com/EPrimeMaster) 
>
> /---- 
> Stock reminder:  1) I do not work for PST.  2) You may reach PST's trained 
> staff (and other support facilities) at https://support.pstnet.com .  3) 
> If 
> you do get an answer from PST staff, please extend the courtesy of posting 
> their reply back here for the sake of others. 
> \---- 
>
>
> At 7/31/2014 10:54 AM Thursday, David Ruvolo wrote: 
> >I have a question regarding using a microphone for measuring RT and 
> >audio input for a battery I am working on. 
> > 
> >I am debating on whether using a audio splitter (a y cable) to send the 
> >signal to the SRBOX and the computer's recording device vs. 
> >using two microphones. If I choose to use two microphones, this creates 
> >extra environmental stimuli, would make positioning the microphones and 
> >testing the setup in the middle of data collection very time consumming 
> >(I am using non SRBOX tasks and SRBOX tasks that have a set order), 
> >this might create inconsistencies with data collection (each individual 
> >has a slightly different positioning, sound doesn't capture, etc), and 
> >the whole experience might be overwhelming for the participant. On the 
> >other hand, using the splitter would eliminate this issue, but I am not 
> >sure if there would result in differences in RT logged by E-Prime (this 
> >would be in ms and could make or break our outcomes). 
> > 
> >Does setup (using a splitter vs. two microphones) effect reaction time? 
> >I would be interested to know if anyone has looked into this, had any 
> >experience using either setup, or measured this.  Feel free to let me 
> >know or tell me I am overthinking this. 
> > 
> >Thanks, 
> > 
> >David 
>
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