Subject: Re: phantom sources From: Enda Bates <enda.bates@xxxxxxxx> Date: Sun, 27 Jul 2014 11:21:18 +0100 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--089e016817deffb1af04ff2a2be1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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 between the localization at low and high frequency ranges, which leads to a slight 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 research 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 the 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 Grantha= m > > 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 community. > > > > 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. cente= r > 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 one= s, > 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 > > > > --=20 www.endabates.net --089e016817deffb1af04ff2a2be1 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <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 local= ization of phantom sources is somewhat frequency dependent. Straightforward= amplitude panning will produce a slight discrepancy between the localizati= on at low and high frequency ranges, which leads to a slight change in timb= re (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 ph= antom 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">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"><br><br><div class=3D"gmail_quote">O= n 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 class=3D"HOEnZb"><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 class=3D"h5"> <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>-- <br><div dir=3D"= ltr"><a href=3D"http://www.endabates.net" target=3D"_blank">www.endabates.n= et</a><br><span style=3D"font-family:arial;font-size:small"><br></span><div= ><br> </div></div> </div> --089e016817deffb1af04ff2a2be1--