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Author Topic: mipro in ears and mics wireless  (Read 6587 times)

Mac Kerr

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Multipath vs Comb filter
« Reply #10 on: April 03, 2011, 04:20:15 pm »

Yes, I meant mulit-path, but what would you say is the difference? I mean - I know it won't create the sound of comb-filtering, but AFAICS it IS comb filtering in the RF-domain in exactly the same way as audio waves do in the air in a different frequency range.

One difference is that comb filtering is a time and frequency based issue that happens over a broad range of frequencies, hence the "comb". Multipath is a similar phase cancellation, but it involves a single frequency.

Mac
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Henry Cohen

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Re: mipro in ears and mics wireless
« Reply #11 on: April 03, 2011, 04:44:42 pm »

Yes, I meant mulit-path, but what would you say is the difference? I mean - I know it won't create the sound of comb-filtering, but AFAICS it IS comb filtering in the RF-domain in exactly the same way as audio waves do in the air in a different frequency range.

Comb filtering is the result of multiple sources (acoustical transducers or speaker cabinets) delivering a broad frequency range of direct energy into the same space at the same time and having the energy levels of the individual frequencies add or subtract due to time arrival differences thus producing an uneven SPL across the reproduced frequency range.

Multi-path occurs when there are multiple propagation paths from a single source (transmit antenna); one direct, the others reflected.

Multi-path is the physical occurrence and does not necessarily have to result in self interference, and in fact does not the vast majority of the time. Comb filtering is the result, and generally a detrimental one.
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Henry Cohen

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Frederik Rosenkjśr

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Re: mipro in ears and mics wireless
« Reply #12 on: April 03, 2011, 06:15:23 pm »

Comb filtering is the result of multiple sources

I don't see why the same source reflecting off walls doesn't qualify as well?

Anyway, I see Mac's point that of course you can't call it "comb" filtering when there's only one point of the graph and not a full comb, but the phenomenon is the same - just different manifestations/descriptions. Either way "multi-path" is certainly a more accurate description of the situation in question.
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Henry Cohen

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Re: mipro in ears and mics wireless
« Reply #13 on: April 04, 2011, 10:57:16 am »

Comb filtering is the result of multiple sources

I don't see why the same source reflecting off walls doesn't qualify as well?

Because reflections are not a source. As I've always understood it, "comb filtering" is the term used to describe the result of direct energy from multiple sources, without reflections considered. Comb filtering occurs in outdoor situations where there are no reflections, thus no multi-path. With that, I'll leave it to the more fluent in acoustical measurement to clarify the matter.
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Henry Cohen

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