The role of acoustic cues in time-­to-­passage judgments : judging time-­to-­passage of looming sounds

5th Iberian Conference on Perception (CIP)
Estimating  the  arrival  of  a  moving  sound  is  part  of  people’s  everyday  tasks,  such  as when  crossing  a  street  with  cars  coming  from  both  sides  (eg.  Winer,  1980  in  Rosenblum, Wuestefeld,  Saldaña,  1993).  Given  equal  distances,  the  beginning  and  ending  positions  of  a moving  sound’s  source  are  perceived  as  closer  when  moving  towards  the  observer  than  when moving  away  (Neuhoff,  2001).This  phenomenon  called  overestimation  of  looming  sounds  has been  recently  studied  with  a  wide  range  of  tasks,  from  discrete  measures  of  loudness  change  to Time-­to-­Arrival  (TTA).
The  aim  of  this  study  is  to  explore  the  ability  of  subjects  to  make  time-­to-­passage  (TTP) judgements  in  an  auditory  perception  task.  White-­noise  (binaural  sound  based  on  interpolated HRTF  in  free-­field)  was  presented  moving  orthogonal  to  the  frontal  plane  along  a  line  that  passed 1  meter  to  the  right  of  the  participant’s  shoulder.  Seven  constant  velocities  were  combined  with
s ev en  initial  dis tanc es ,  res ulting  into  49  lev els  of  TTP ,  24  arriv ing  one  s ec ond  before  pas s age and  24  after  (see  Mouta,  Santos,  López-­Moliner,  2012).  Subjects  had  to  decide  whether  an approaching  sound  passed  by  the  ear  plane  before  or  after  the  reference  time  (1s).  In  a  first experiment  we  intended  to  analyse  whether  the  overestimation  of  looming  sounds  would  occur. Following  previous  studies  on  this  phenomenon  with  loudness  change  (Neuhoff,  2001)  and  with a  TTA  task  (Rosenblum,  Wuestefeld,  Saldaña,  1993)  we  also  expected  to  find  overestimation. Results  showed  that  subjects  were  able  to  judge  TTP  (R2=  0.95).  Although,  regarding overestimation,  a  clear  pattern  was  not  found  on  individual  data.  We  also  raised  the  question  of whether  participants  could  make  judgements  when  the  stimuli  would  not  be  completely presented,  using  an  occlusion  period  (at  0.5,  0.7  and  0.9s  of  stimulus  presentation).  Participants were  instructed  to  estimate  passage,  at  the  moment  signalized  by  a  temporal  marker  (a  beep, always  presented  1s  after  the  beginning  of  the  stimulus  presentation),  assuming  that  velocity and  trajectory  remained  constant.  Our  expectation  was  to  find  a  deterioration  pattern  as  the occlusion  period  increased.  Results  did  not  verify  this  last  hypothesis.  Accuracy  and  precision did  not  vary  with  different  occlusion  periods,  although  adjustment  values  were  lower  for  the condition  with  higher  occlusion  period  (R2=  0.73)  and  higher  for  the  one  with  lower  occlusion period  (R2=  0.86).
All  in  all,  we  did  not  find  the  overestimation  pattern  reported  in  the  literature,  even  with stimulus  occlusion,  at  least  with  this  kind  of  task  and  stimuli.