Thursday, May 2, 2013

Interview with Gurjit Singh on Binaural Listening

Gurjit Singh, Senior Research Audiologist from Phonak AG headquarters talks about the benefits of Phonak’s Binaural VoiceStream TechnologyTM. This hearing instrument feature from Phonak mimics the effects of binaural listening, in order to improve speech understanding and listening effort, in environments which are difficult for people with hearing impairment. This technology determines at which ear there is a better signal-to-noise ratio. The full audio signal from this ear is then streamed to the other ear, where the signal-to-noise ratio is poorer. There are two main benefits of this: binaural summation and binaural redundancy. 

Video Transcript:

Anna: Gurjit, would you mind elaborating a little bit more as to why listening with two ears is important?

Gurjit: It’s important for almost all the auditory tasks that we engage in. It’s important for speech understanding in noise. It’s important for localization abilities, listening in complex listening environments of the sort that are difficult for people with hearing impairment. Listening with two ears takes advantage of a number of mechanisms that help us to better understand speech. One of my favorites that we are studying these days is looking at the effect of listening effort and how it is minimized once you are listening with two ears. 

Anna: With regards to Phonak’s Binaural VoiceStream Technology within the hearing instruments, how do we help or how do we use Binaural VoiceStream Technology to somehow mimic or to create these effects? 

Gurjit: Binaural VoiceStream is really closely coupled with the sensors that we have for classifying the environment, and so it is critically dependent on finding an ear where there is a better signal-to-noise ratio. Wherever there is that better signal-to-noise ratio, a copy is then streamed to the other ear, where there is a poorer signal-to-noise ratio. This is a facet of listening for normal hearing and it’s what we do best, in terms of un-masking of speech and this is what we’re trying to mimic and enhance with Binaural VoiceStream Technology. But there are other effects as well, but I’m sure we’ll get into that in a second. 

Anna: In your insight that you wrote ‘Listening with two ears instead of one’ you explain how listening improves with full audio streaming between hearing instruments. Could you just elaborate a bit further as to how that happens? 

Gurjit: Yeah sure, no problem. The ability to stream a signal from one ear to another really represents a technological leap and that’s because when you’re in a complex listening environment, there’s often a better signal-to-noise ratio at one ear relative to the other. Because of our classifier, we are make to make that detection and then we send where the signal is better, to the other ear. This is really important for two reasons: The first reason it that you will experience a summation, because you will have the same signal in both ears and that results in an increased percept of that target signal. This is called binaural loudness summation. The other effect is binaural redundancy. What I mean by that is, the ear has multiple opportunities to capture the cues that are available in a signal. So, if you have a different hearing loss between the ears, you might get some of the cues with one ear, and other cues with the other ear. 
Anna: In conclusion, could you just sum up for me in your own way, the advantages of Binaural VoiceStream Technology. 

Gurjit: You know, it’s really interesting because for over 50 years we have been conducting research in hearing looking at basic psychoacoustic phenomena. We’ve understood a lot about the ear, but up until now we haven’t really known how to apply much of that finding, much of this research, to technology. But, now that we have the capability to wirelessly stream a full audio signal from one ear to another, we can start to take advantage of all that we have learned over the past 50 years. But, the primary benefit is that we are assessing where there is a better signal-to-noise ratio at one ear and sending that signal to the other ear. This takes advantage of binaural loudness summation, hearing a signal with both ears and having that increased percept of loudness. If you have ever talked on the cellphone and you’ve listened with one ear and then you’ve listened with that same cellphone connected to both ears, it is so much easier, and that is the type of benefit that you experience with Binaural VoiceStream Technology.