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Bass limitations with my Cochlear Implant

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Bass limitations with my Cochlear Implant

Postby garrettendi » Fri Aug 09, 2019 1:49 pm

I have Melda's MDrummer that comes with almost the complete collection of Melda plugins to use (only) within MDrummer itself. I had the bright idea of using MBassador to add sub-bass to the kick drum to give it a bit of oomph.

But therein lies the rub. I've since learned that my Cochlear Implant only goes down to 100Hz. I did some research and found out a bass guitar goes down to somewhere around 44Hz and a piano even lower. I listened to the E1 tone of a bass guitar and the A0 tone of a piano and found I could hear them, but a sine wave at E1 I couldn't hear at all.

So what's happening here? I know if I use an analyser on a bass guitar sound, there's all kinds of things going on over 100Hz. So my theory is that I'm actually hearing those frequencies of the bass, as if it had a HPF set to 100Hz.

Which leads to my next question. How can I overcome this when mixing? There's going to be so much happening in the lower range that I just won't be able to hear. I can get someone with natural hearing to review my mixes, but do you guys have any ideas as to how I can get a decent result before I involve someone else?
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Re: Bass limitations with my Cochlear Implant

Postby Exalted Wombat » Fri Aug 09, 2019 2:26 pm

Yes, we often actually hear the overtones of a low note, our brains derive the fundamental from them. And very useful this is too - enabling bass lines to be heard without the size and power requirements of actually shifting air at sub-40Hz frequencies! It lets church organ designers use a few ranks of small pipes ("Acoustic bass") rather than a rank of HUGE ones. And it let us listen to rock music from Radio Caroline in the 1960s on our transistor radios with SOME idea of what the bass was doing!


However. Some playback systems and some styles of music DO feature real low-frequency content, and it seems you aren't equipped to hear it directly. Metering and spectrum analysis will help - we all use it to check for (often unwanted) content in the sub-audible range. It will help you tell if SOMETHING is happening in that range. Hopefullly you will learn to correlate what you see on the spectrum display with what others tell you they hear.
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Re: Bass limitations with my Cochlear Implant

Postby Hugh Robjohns » Fri Aug 09, 2019 3:35 pm

garrettendi wrote:I've since learned that my Cochlear Implant only goes down to 100Hz.

This is not really surprising as I assume it is designed primarily for conveying speech and there's nothing of value in speech below 100Hz or so...

I listened to the E1 tone of a bass guitar and the A0 tone of a piano and found I could hear them, but a sine wave at E1 I couldn't hear at all. So what's happening here?

Normal musical tones have harmonics, and so even if you can't hear the fundamental -- or if a loudspeaker can't reproduce the fundamental (such as a small pocket radio etc) -- your ear/brain will hear the harmonics and effectively synthesise the missing fundamental in your cognitive listening process. In other words, we imagine what the fundamental must have been given the harmonics we can here. This is how we can tolerate listening to music on things with small speakers!

How can I overcome this when mixing? There's going to be so much happening in the lower range that I just won't be able to hear. I can get someone with natural hearing to review my mixes, but do you guys have any ideas as to how I can get a decent result before I involve someone else?

My advice would be, if in doubt, leave the bass end alone! And second to that, learn to interpret what you can see on a spectrum (or better still, an FFT) analyser. And yes, get a friend to listen and comment.

There are some folks who claim to be able to tell a lot about the bass end by resting a finger on the edge of the woofer in their speakers... but it make take considerable practice to master that one! ;-)

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Re: Bass limitations with my Cochlear Implant

Postby garrettendi » Fri Aug 09, 2019 4:16 pm

Thanks to both of you!

I'm glad that I'm not going crazy - that bass did definitely sound "bassy"! The brain is a marvellous thing indeed.

I've got a few analyser plugins knocking about and possibly an FFT. I'll see what I can unearth in my VST Plugins folder.

As you say Hugh, it seems to make sense to leave the bass alone if I don't know what I'm doing. I'll also take Exalted's suggestion of learning to read the analysis, possibly with the help of a friend who can be my ears along with my own eyes.
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Re: Bass limitations with my Cochlear Implant

Postby James Perrett » Fri Aug 09, 2019 8:35 pm

Hugh Robjohns wrote:There are some folks who claim to be able to tell a lot about the bass end by resting a finger on the edge of the woofer in their speakers... but it make take considerable practice to master that one! ;-)

That's where the white cones on NS10's come in handy - you can't hear the bass on them but you can see it fairly easily.
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Re: Bass limitations with my Cochlear Implant

Postby Tim Gillett » Fri Aug 09, 2019 10:35 pm

There are probably very good reasons why it was set up that way but in your case maybe you could enquire whether your cochlear implant circuitry could be slightly modified to include that lower octave or so, at least as a user switchable option. When I worked in hearing aids, some aids featured a switchable hpf. Switching it out gave better lf extension but went through the batteries quicker!
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Re: Bass limitations with my Cochlear Implant

Postby garrettendi » Fri Aug 09, 2019 11:10 pm

I may enquire but I think it’s actually a limitation of the internal electrodes which nothing can be done about.

Last time I told them about my home studio and music they enabled a two band EQ (just bass and treble) though. That has made a real difference so it’s worth an ask.

Hugh is right though. CIs are designed primarily with speech in mind. Even the external device is called the Speech Processor. An experience like mine with music is rare.
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Re: Bass limitations with my Cochlear Implant

Postby Hugh Robjohns » Sat Aug 10, 2019 10:27 am

garrettendi wrote:I may enquire but I think it’s actually a limitation of the internal electrodes which nothing can be done about.

Low frequencies are sensed towards the tip of the Cochlear, and I imagine it's pretty difficult to get the implant that far into it, hence the practical limitation in how low a frequency it can stimulate.

...at a guess...

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Re: Bass limitations with my Cochlear Implant

Postby Arpangel » Sat Aug 10, 2019 10:47 am

I would use a track that has been listened to by someone you trust, and who understands your music, as a reference on a spectrum analyser. It's not ideal, but....
Also, just a mention, don't be tempted to turn the volume up, keep listening levels at a sensible level.
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Re: Bass limitations with my Cochlear Implant

Postby Wonks » Sat Aug 10, 2019 11:45 am

garrettendi wrote:I've got a few analyser plugins knocking about and possibly an FFT. I'll see what I can unearth in my VST Plugins folder.

Best to use a bar-graph style analyser than an oscilloscope type display for looking at real-time bass-end information. The sampling time window for real-time display is too short for accurate FFT analysis at bass frequencies, so you end up with very poor representation of bass levels. You can put a 128dB/octave HPF at 60Hz and an oscilloscope display will still show a hefty amount of bass at say 30Hz, which simply isn't there. A bar-graph type meter works in a different way and is far more accurate, though you do suffer from having fixed frequency band displays, so you can't be as clinical.

For really detailed analysis, you need to work off-line. Select a few seconds of material and use the DAW tools to do a frequency analysis. This should then show a pretty accurate frequency picture - but it will be an average value for that time period, so don't choose a section of music with just one note in it!
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