Subject: Re: phantom sources From: James Johnston <audioskeptic@xxxxxxxx> Date: Sun, 27 Jul 2014 22:50:30 -0700 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--001a11c3612233359f04ff3a806b Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Well, having read more than one paper saying that there are no time cues above 2kHz (or 3kHz, take your choice) I offer everyone the following challenge. Take a pulse train at maybe 100Hz. Filter it with a standard elliptic HP so that there is no energy to speak of below 2kHz (or 3, your choice). LIsten to it time synced in stereo. Listen to it with a 2 sample delay in one channel, identical signals, identical levels, i.e. copy with 2 sample delay into one channel. In speakers, tell me that they don't sound different. In headphones, ditto. I have recently seen some scathing, and completely wrong, reviews arising from some 1955 tests that attempted time-delay pan, using increments of 5 milliseconds. Rather obviously, unless your head is 5 feet wide, 5 milliseconds is excessively too much. So, be careful with the literature out there, rather some of it can be disproven with a very simple matlab example. JJ On Sun, Jul 27, 2014 at 3:21 AM, Enda Bates <enda.bates@xxxxxxxx> wrote: > Hi Philip, > yeah there's been quite a bit of work on this type of thing in > audio research. You are also basically correct in that a phantom source > will be a little broader than a real source, largely due to the fact that > the localization of phantom sources is somewhat frequency dependent. > Straightforward amplitude panning will produce a slight discrepancy betwe= en > the localization at low and high frequency ranges, which leads to a sligh= t > change in timbre (manifests as a slight spectral dip at approx. 2kHz) and > an increase in the Apparent Source Width (ASW) of the source when it is > reproduced as a phantom image. > > This is a big problem when dynamically panning a sound as this change in > timbre tends to highlight the loudspeakers in a negative way and it > significantly reduces the smoothness of the spatial trajectory > (incidentally, one the main goals of the Ambisonics spatialization system > was to eliminate this issue, which it largely does but not without some > costs). > > Ville Pullki has done a lot of research in this area, particularly in > terms of his amplitude panning system VBAP. He has also conducted researc= h > on panning using three loudspeakers (again with VBAP). My recollection is > that this will increase the ASW even further, and similarly reduce > localization accuracy. Of course there is a strong relationship between t= he > two factors, and the concept of locatedness is useful in this regard. > > Anyway, chapter 6 my PhD thesis has lots of specific references in terms > of listening tests with phantom sources and the relationship between > localization accuracy and apparent source width, both for stereophony and > ambisonics. You can find it here -> http://endabates.net/academic.html > > Hope that helps, > Dr. Enda Bates > Music & Media Technology, > Trinity College Dublin > > > > > > > > > On 26 July 2014 16:45, William Yost <William.Yost@xxxxxxxx> wrote: > >> Fine work in Journal of the Acoustical Society of America by Wes >> Grantham >> >> Sent from my IPhone >> William Yost >> William.yost@xxxxxxxx >> Office: 480-727-7148 >> Home: 480-306-6755 >> Cell: 480-231-9250 >> >> >> >> On Jul 25, 2014, at 9:17 PM, "Philip Robinson" <philrob22@xxxxxxxx> >> wrote: >> >> Howdy y=E2=80=99all, >> >> >> >> I=E2=80=99m doing some investigations preliminary to implementing a room >> acoustics auralization system and want to get some input from the commun= ity. >> >> >> >> Is there any good literature on the perceptual difference between a >> phantom source (e.g. between a stereo pair) and a real source (e.g. cent= er >> channel)? I am interested in more than just simple localization: width, >> resolution of multiple phantoms, etc.? Is perception of a phantom source >> the same when panned between a triad or a pair of loudspeakers? My basic >> understanding is that phantom sources are wider or blurrier than real on= es, >> has this been specifically tested? >> >> >> >> Any opinions or references are welcome. >> >> >> >> Have a great summer, >> >> >> >> *Philip W. Robinson * >> >> *Environmental Design Analyst* >> >> *Specialist Modelling Group* >> >> >> >> Foster + Partners >> >> Riverside, 22 Hester Road >> >> London SW11 4AN >> >> E probinson@xxxxxxxx >> >> >> >> > > > -- > www.endabates.net > > > --=20 James D. (jj) Johnston Independent Audio and Electroacoustics Consultant --001a11c3612233359f04ff3a806b Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr">Well, having read more than one paper saying that there ar= e no time cues above 2kHz (or 3kHz, take your choice) I offer everyone the = following challenge.<br><br>Take a pulse train at maybe 100Hz.=C2=A0 Filter= it with a standard elliptic HP so that there is no energy to speak of belo= w 2kHz (or 3, your choice).<br> <br>LIsten to it time synced in stereo.<br><br>Listen to it with a 2 sample= delay in one channel, identical signals, identical levels, i.e. copy with = 2 sample delay into one channel.<br><br>In speakers, tell me that they don&= #39;t sound different.<br> In headphones, ditto.<br><br>I have recently seen some scathing, and comple= tely wrong, reviews arising from some 1955 tests that attempted time-delay = pan, using increments of 5 milliseconds.<br><br>Rather obviously, unless yo= ur head is 5 feet wide, 5 milliseconds is excessively too much.<br> <br>So, be careful with the literature out there, rather some of it can be = disproven with a very simple matlab example.<br><br>JJ<br></div><div class= =3D"gmail_extra"><br><br><div class=3D"gmail_quote">On Sun, Jul 27, 2014 at= 3:21 AM, Enda Bates <span dir=3D"ltr"><<a href=3D"mailto:enda.bates@xxxxxxxx= il.com" target=3D"_blank">enda.bates@xxxxxxxx</a>></span> wrote:<br> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div>Hi Philip,</div><div>= =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0yeah there's been quite a bit of work= on this type of thing in audio research. You are also basically correct in= that a phantom source will be a little broader than a real source, largely= due to the fact that the localization of phantom sources is somewhat frequ= ency dependent. Straightforward amplitude panning will produce a slight dis= crepancy between the localization at low and high frequency ranges, which l= eads to a slight change in timbre (manifests as a slight spectral dip at ap= prox. 2kHz) and an increase in the Apparent Source Width (ASW) of the sourc= e when it is reproduced as a phantom image.=C2=A0</div> <div><br></div><div>This is a big problem when dynamically panning a sound = as this change in timbre tends to highlight the loudspeakers in a negative = way and it significantly reduces the smoothness of the spatial trajectory (= incidentally, one the main goals of the Ambisonics spatialization system wa= s to eliminate this issue, which it largely does but not without some costs= ).=C2=A0</div> <div><br></div><div>Ville Pullki has done a lot of research in this area, p= articularly in terms of his amplitude panning system VBAP. He has also cond= ucted research on panning using three loudspeakers (again with VBAP). My re= collection is that this will increase the ASW even further, and similarly r= educe localization accuracy. Of course there is a strong relationship betwe= en the two factors, and the concept of locatedness is useful in this regard= .=C2=A0</div> <div><br></div><div>Anyway, chapter 6 my PhD thesis has lots of specific re= ferences in terms of listening tests with phantom sources and the relations= hip between localization accuracy and apparent source width, both for stere= ophony and ambisonics. You can find it here ->=C2=A0<a href=3D"http://en= dabates.net/academic.html" target=3D"_blank">http://endabates.net/academic.= html</a></div> <div><br></div><div>Hope that helps,</div><div>Dr. Enda Bates</div><div>Mus= ic & Media Technology,</div><div>Trinity College Dublin</div><div><br><= /div><div><br></div><div><br></div><div><p class=3D"MsoNormal" style=3D"mar= gin:0cm 0cm 0.0001pt;font-family:arial,sans-serif;font-size:13px"> <br></p><p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt;font-family= :arial,sans-serif;font-size:13px"><br></p><p class=3D"MsoNormal" style=3D"m= argin:0cm 0cm 0.0001pt;font-family:arial,sans-serif;font-size:13px"><u></u>= =C2=A0</p> </div></div><div class=3D"gmail_extra"><div><div class=3D"h5"><br><br><div = class=3D"gmail_quote">On 26 July 2014 16:45, William Yost <span dir=3D"ltr"= ><<a href=3D"mailto:William.Yost@xxxxxxxx" target=3D"_blank">William.Yost= @xxxxxxxx</a>></span> wrote:<br> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex"> <div dir=3D"auto"> <div>Fine work in Journal of the Acoustical Society of America by Wes Grant= ham<br> <br> Sent from my IPhone <span><font color=3D"#888888"><div>William Yost</div> <div><a href=3D"mailto:William.yost@xxxxxxxx" target=3D"_blank">William.yost= @xxxxxxxx</a></div> <div>Office: <a href=3D"tel:480-727-7148" value=3D"+14807277148" target=3D"= _blank">480-727-7148</a></div> <div>Home: <a href=3D"tel:480-306-6755" value=3D"+14803066755" target=3D"_b= lank">480-306-6755</a></div> <div>Cell: <a href=3D"tel:480-231-9250" value=3D"+14802319250" target=3D"_b= lank">480-231-9250</a></div> <div><br> </div> <div><br> </div> </font></span></div><div><div> <div><br> On Jul 25, 2014, at 9:17 PM, "Philip Robinson" <<a href=3D"mai= lto:philrob22@xxxxxxxx" target=3D"_blank">philrob22@xxxxxxxx</a>> wrot= e:<br> <br> </div> <blockquote type=3D"cite"> <div> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><span style=3D"bac= kground-color:rgba(255,255,255,0)">Howdy y=E2=80=99all,<u></u><u></u></span= ></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><u></u>=C2=A0<u></= u></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><span style=3D"bac= kground-color:rgba(255,255,255,0)">I=E2=80=99m doing some investigations pr= eliminary to implementing a room acoustics auralization system and want to = get some input from the community.<u></u><u></u></span></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><u></u>=C2=A0<u></= u></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><span style=3D"bac= kground-color:rgba(255,255,255,0)">Is there any good literature on the perc= eptual difference between a phantom source (e.g. between a stereo pair) and a real source (e.g. center channel)? =C2=A0I am interested in more than ju= st simple localization: width, resolution of multiple phantoms, etc.? Is pe= rception of a phantom source the same when panned between a triad or a pair= of loudspeakers? My basic understanding is that phantom sources are wider or blurrier than real ones, has this bee= n specifically tested?<u></u><u></u></span></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><u></u>=C2=A0<u></= u></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><span style=3D"bac= kground-color:rgba(255,255,255,0)">Any opinions or references are welcome.<= u></u><u></u></span></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><u></u>=C2=A0<u></= u></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><span style=3D"bac= kground-color:rgba(255,255,255,0)">Have a great summer,<u></u><u></u></span= ></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><u></u>=C2=A0<u></= u></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><span style=3D"bac= kground-color:rgba(255,255,255,0)"><b>Philip W. Robinson=C2=A0</b></span></= p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><b style=3D"backgr= ound-color:rgba(255,255,255,0)">Environmental Design Analyst<u></u><u></u><= /b></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><span style=3D"bac= kground-color:rgba(255,255,255,0)"><b>Specialist Modelling Group</b><u></u>= <u></u></span></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><span style=3D"bac= kground-color:rgba(255,255,255,0)">=C2=A0<u></u><u></u></span></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><span style=3D"bac= kground-color:rgba(255,255,255,0)">Foster + Partners<u></u><u></u></span></= p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><span style=3D"bac= kground-color:rgba(255,255,255,0)">Riverside,=C2=A0<a>22 Hester Road</a><u></u><u></u></span></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><font color=3D"#00= 0000"><span style=3D"background-color:rgba(255,255,255,0)"><a>London SW11 4AN</a><u></u><u></u></span></font></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><span style=3D"bac= kground-color:rgba(255,255,255,0)">E=C2=A0=C2=A0<a href=3D"mailto:probinson= @xxxxxxxx" target=3D"_blank">probinson@xxxxxxxx</= a><u></u><u></u></span></p> <p class=3D"MsoNormal" style=3D"margin:0cm 0cm 0.0001pt"><u></u>=C2=A0<u></= u></p> </div> </blockquote> </div></div></div> </blockquote></div><br><br clear=3D"all"><div><br></div></div></div><span c= lass=3D"HOEnZb"><font color=3D"#888888">-- <br><div dir=3D"ltr"><a href=3D"= http://www.endabates.net" target=3D"_blank">www.endabates.net</a><br><span = style=3D"font-family:arial;font-size:small"><br> </span><div><br> </div></div> </font></span></div> </blockquote></div><br><br clear=3D"all"><br>-- <br><div>James D. (jj) John= ston</div><div>Independent Audio and Electroacoustics Consultant</div> </div> --001a11c3612233359f04ff3a806b--