across channel Flashcards
frequency resolution
The ability to separate out one component in a complex sound
into auditory filters
to across-channel processing
across-channel processing
Interactions among or comparisons across separate frequency channels that affect auditory performance
(this starts how people put the info back together)
aid detection examples of across-channel processing
psychophysical two-tone suppression; comodulation masking release (CMR); profile analysis
impair detection examples of across-channel processing
modulation detection interference (MDI); psychophysical overshoot
psychophysical two-tone suppression
(mach bands are a visual case of this)
Masker tone freq and level are fixed.
suppressor tone level is fixed, but its freq is varied across tests to form the curve
the detection threshold for the forward-masked signal is determined: in the 1.presence of only the masker tone (horizontal straight line) and 2. in the presence of the masker + suppressor (points on the curve)
a lower threshold in 2 than 1 shows suppression.
suppression was defined as the difference in forward-masking thresholds measured in he narrowest and widest bandpass
Young have more suppression
Old with normal hearing still have some suppression
The greater the HL the more suppression is lost.
So w/o suppression process, you cant mark the edges correctly. Cant Keep things narrow. So spectrum gets more smeared
comodulation masking release
Your job is to detect signal in a masker. Trick is that top one has a flat envelope and the signal is inside of that. On the other hand, they amp modulate the noise. So the noise goes up and down in level and the tone is still inside that. They manipulate the bandwidth of the masker.
Narrower bandwith = threshold goes up and gets flat.
Now its narrow band of noise and the masker goes up and down in level/modulated. Detect the tone! As the bandwidth increases, the threshold goes up just like before. Why? Youre filling up more of the filter/more to deal with so it gets more difficult. As you increase the modulated noise even wider, the threshold drops. When the masker is wide, the threshold can be 10 dB lower than the unmodulated masker. Basically up until now you had a critical band you increase and then plateau. BUT the more channels you get, it doesn’t work the same.
If youre listening for a tone in a noise, whens a good time to listen to it in a fluctuating noise? When the noise is the smallest. So they talk about peaks in noise and valleys in noise. So one idea is dip listening: people are trying to listen in the dip of the noise to get the best shot of hearing the signal. wouldn’t it be useful if you had something off to the side to tell you when the dip was…
CMR and hearing loss
CMR = unmodulated – modulated noise.
CMR is lower with people with hearing loss. Why? Critical band gets wider. Why does that make CMR go away? Cuz the CUE band is going into the other one cuz the filter is wider. So you’ve lost the independent information when the bands overlap.
Big number means youre getting a lot of modulation.
profile analysis
How do you tell the diff between levels of individual components in a spectrum?
You’d have to realize that the 2 points are at different levels.
2 possible ways of thinking about this:
Classic way. What you do is you literally pay attention to/focus in on 1 freq and get a reading and then get the next presentation and you get another measure and then you comepare the two. So u get 1 measure in the first observation and a 2nd measure in a 2nd observation and then compare.
maybe what you’re doing is comparing inside 1 observation the stimulus levels at 2 different positions. So you maybe care about it but you compare it to the neighbor next to you. When you get to the 2nd observation you make the same comparison. So youre looking at the profile (spectrum of a stimulus..like a side view of someones face) and analyzing the shape/levels based on the neighbor levels.
modulation detection interference
Job is to detect the depth in the modulation. What they’re measuring is the smallest change in the depth that you can detect. So how close can you get to 0, and not be 0, and still be able to tell different depths ((we mean 0 in terms of depth. So flat))
You have a modulated tone and then you also have an ongoing tone that’s not modulated at the same time.
Selectviity: you don’t care about the first round with 2 tones. If you do the same experiement but make the other tone amp modulated instead of steady, then you really have a difficult time detecting the modulation. So if youre listening to 10 hz modulation in 1 freq band and 10 hz modulation in the other band, its hard to distinguish the modulation.
When the rate of modulation is different, the threshold drops again.
So what can we tell about modulation detection from this example? What can we tell by the diff between the modulated masker same rate vs modulated masker different rate? You get the info and you have to really think thru it. Is it possible that there is more than 1 filter in the brain? Yes! Is likely that there are modulation filters..that care about different rates of modulations…let one rate thru and not another one.
overshoot
The detection threshold for a simultaneously masked signal is determined at different temporal positions in the masking sound.
Threshold is highest when the signal is presented at the very beginning of the masker. This is psychophysical overshoot.
In HL overshoot is lost because people with HL don’t have bad performance in the beginning. They also lose chance of detecting lots of info.
