Reaction time measures of phantom image recognition in stereophonic listening

Intensity stereophony allows the listener to perceive phantom images, which may be localized at any point on the imaginary soundstage existing between loudspeaker pairs. Specification of the phantom image typically relies on subjective evaluation by the listener. This study utilized reaction time to quantify the ability of listeners to accurately identify the image position as a function of frequency. Subjects were seated at 30‐deg incidence to each loudspeaker in an anechoic environment. Each trial consisted of a pair of third‐octave noise bursts at one of six frequencies (250–8000 Hz). The first of each stimulus pair was presented with no interloudspeaker intensity difference (phantom center). The second stimulus occurred randomly at phantom center, phantom left, or phantom right, and subjects were instructed to correctly respond as quickly as possible in this three‐choice forced response task. Interloudspeaker intensity difference for images occurring left or right of center was 2, 4, or 6 dB. Longer reaction times occurred for center image responses, independent of frequency. Shortest reaction times were obtained at 2 kHz, with increasing latencies occurring at higher frequencies. Data suggests that phantom image identification in stereophonic listening is compromised above 2 kHz.