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Sursound Digest, Vol 121, Issue 13
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Florian Grond
2018-08-28 13:07:52 UTC
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Hi everyone,

Regarding the question of which mems the ZM-1 uses, here is some detailed
info I just found:
https://www.infineon.com/cms/en/about-infineon/press/market-news/2018/INFPMM201808-078.html

Best,

Florian



www.grond.at


On Sat, Aug 18, 2018 at 12:00 PM <sursound-***@music.vt.edu> wrote:

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> Today's Topics:
>
> 1. MEMS SNR Specifications (Ralph Jones)
> 2. Re: MEMS SNR Specifications (Paul Hodges)
> 3. Re: MEMS SNR Specifications (Jack Reynolds)
> 4. Re: MEMS SNR Specifications (Bo-Erik Sandholm)
> 5. Re: MEMS SNR Specifications (Chris Woolf)
> 6. Re: MEMS SNR Specifications (Fons Adriaensen)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 17 Aug 2018 14:55:36 -0700
> From: Ralph Jones <***@comcast.net>
> To: ***@music.vt.edu
> Subject: [Sursound] MEMS SNR Specifications
> Message-ID: <3EF51B54-D429-4DEF-8ADD-***@comcast.net>
> Content-Type: text/plain; charset=utf-8
>
> There?s been some interesting discussion here about
> Micro-ElectroMechanical Systems (MEMS) microphones for ambisonic mic
> arrays. These devices seem to offer some compelling qualities (particularly
> small size and low cost) but their signal-to-noise spec is 65 dBA. Some
> folks posting here have seemed to suggest that this level of noise might
> possibly be acceptable.
>
> IMHO, based on decades of experience, a microphone with a signal-to-noise
> ratio of 65 dBA is useless for professional recording. That's in the SNR
> range typical of consumer cassette tape machines or analog AM radio.
>
> For comparison, consider that professional large-diaphragm condenser mics
> achieve 120-130 dB SNR. The Sennheiser Ambeo has an SNR of about 110 dB.
> Portable digital audio recorders and popular audio interfaces make about
> 100 dB, and Red Book CDs 98 dB. Even vinyl records are about 6 dB quieter
> than MEMS mic elements.
>
> Put a MEMS mic at the input of a digital recorder and you?re wasting 35 dB
> of dynamic range (not to mention the case of using several of them in an
> ambisonic array). That?s huge. A symphony orchestra playing at mezzoforte
> or louder may mask the noise if the mic is reasonably close to the stage,
> but forget trying to record softer passages. Recordists trying to capture
> natural ambiences will be sorely disappointed; a lot of what they?re trying
> to record will simply disappear into the noise floor. You might get away
> with using it for non-critical functions like background crowd noise for
> telecasts of sporting events, but that?s about it.
>
> MEMS mics appear to me to have been developed for applications that
> require very small size, physical ruggedness, reasonable frequency response
> and low cost, but can tolerate a high noise floor. There are lots of such
> use cases, but professional audio is not one of them. If we wish to advance
> the art of ambisonic recording and reproduction, we cannot compromise basic
> performance specifications for the sake of a trendy idea.
>
> Ralph Jones
>
> ------------------------------
>
> Message: 2
> Date: Fri, 17 Aug 2018 23:56:21 +0100
> From: Paul Hodges <pwh-***@cassland.org>
> To: Surround Sound discussion group <***@music.vt.edu>
> Subject: Re: [Sursound] MEMS SNR Specifications
> Message-ID: <959BC7A058AAE6865F337CAC@[192.168.1.74]>
> Content-Type: text/plain; charset=us-ascii
>
> --On 17 August 2018 14:55 -0700 Ralph Jones <***@comcast.net>
> wrote:
>
> > Some folks posting here have seemed to suggest that this level of
> > noise might possibly be acceptable.
>
> Well, firstly we don't know the actual specification of the devices
> used by Zylia. And secondly, using an array of nineteen to generate an
> output gives the possibility of significant improvement, because the
> sound source signals are correlated and the noise is uncorrelated.
>
> How this holds up in practice at higher orders and higher frequencies I
> will attempt to judge when I get my hands on the ZM-1 rather than just
> predicting failure in advance (which is not consistent with the reviews
> I've seen heard and read).
>
> Paul
>
> --
> Paul Hodges
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 18 Aug 2018 00:37:22 +0100
> From: Jack Reynolds <***@gmail.com>
> To: Surround Sound discussion group <***@music.vt.edu>
> Subject: Re: [Sursound] MEMS SNR Specifications
> Message-ID: <918D363C-EB4C-42BC-81D7-***@gmail.com>
> Content-Type: text/plain; charset=us-ascii
>
> Are you sure the Ambeo has 110dB SNR?
>
> Sent from my iPhone
>
> > On 17 Aug 2018, at 23:56, Paul Hodges <pwh-***@cassland.org> wrote:
> >
> > --On 17 August 2018 14:55 -0700 Ralph Jones <***@comcast.net>
> > wrote:
> >
> >> Some folks posting here have seemed to suggest that this level of
> >> noise might possibly be acceptable.
> >
> > Well, firstly we don't know the actual specification of the devices
> > used by Zylia. And secondly, using an array of nineteen to generate an
> > output gives the possibility of significant improvement, because the
> > sound source signals are correlated and the noise is uncorrelated.
> >
> > How this holds up in practice at higher orders and higher frequencies I
> > will attempt to judge when I get my hands on the ZM-1 rather than just
> > predicting failure in advance (which is not consistent with the reviews
> > I've seen heard and read).
> >
> > Paul
> >
> > --
> > Paul Hodges
> >
> > _______________________________________________
> > Sursound mailing list
> > ***@music.vt.edu
> > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
>
>
> ------------------------------
>
> Message: 4
> Date: Sat, 18 Aug 2018 09:41:13 +0200
> From: Bo-Erik Sandholm <***@gmail.com>
> To: sursound <***@music.vt.edu>
> Subject: Re: [Sursound] MEMS SNR Specifications
> Message-ID:
> <CAEAiL24g=oFicUeY4cjyxxGebA7YPnP3ZHSmRN9Hp3gFoW+==
> ***@mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> According to the document linked to below that relates self noise values to
> real world applications 110 SNR cannot be related to the commonly used
> reference sound level.
> 110 dBA SNR would be 16 dB below absolute quiet.
>
> If the value 70dBA that I found for the infineon dual membrane MEMS mic is
> related to 1 Pascal, then it's self noise is around 24 dB which is not
> strictly studio quality.
> But not really horrible.
> If it is related to max 10% distortion which is at 135 dBA thats not a
> realistic comparison value as the result is a self noise of 65 dBA.
>
> That would be a noise source not a microphone :-) !
>
> So a bit of apples and oranges comparison is going on ??
>
>
>
> http://www.neumann.com/homestudio/en/what-is-self-noise-or-equivalent-noise-level
>
> SIGNAL-TO-NOISE RATIO
> Another way to document the noise performance is to specify the
> signal-to-noise ratio. But relative to what signal? The reference sound
> pressure level for noise measurements is 94 dB (which equals a sound
> pressure of 1 pascal). So you can simply calculate:
>
> Signal-to-noise (db-A) = 94 dB ? self-noise (dB-A)
>
>
>
> The actual signal-to-noise ratio in use, of course, depends on the sound
> pressure level of your sound source.
>
>
> Bo-Erik
>
> On Sat, 18 Aug 2018 01:37 Jack Reynolds, <***@gmail.com>
> wrote:
>
> > Are you sure the Ambeo has 110dB SNR?
> >
> > Sent from my iPhone
> >
> > > On 17 Aug 2018, at 23:56, Paul Hodges <pwh-***@cassland.org>
> wrote:
> > >
> > > --On 17 August 2018 14:55 -0700 Ralph Jones <***@comcast.net>
> > > wrote:
> > >
> > >> Some folks posting here have seemed to suggest that this level of
> > >> noise might possibly be acceptable.
> > >
> > > Well, firstly we don't know the actual specification of the devices
> > > used by Zylia. And secondly, using an array of nineteen to generate an
> > > output gives the possibility of significant improvement, because the
> > > sound source signals are correlated and the noise is uncorrelated.
> > >
> > > How this holds up in practice at higher orders and higher frequencies I
> > > will attempt to judge when I get my hands on the ZM-1 rather than just
> > > predicting failure in advance (which is not consistent with the reviews
> > > I've seen heard and read).
> > >
> > > Paul
> > >
> > > --
> > > Paul Hodges
> > >
> > > _______________________________________________
> > > Sursound mailing list
> > > ***@music.vt.edu
> > > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe
> here,
> > edit account or options, view archives and so on.
> > _______________________________________________
> > Sursound mailing list
> > ***@music.vt.edu
> > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> > edit account or options, view archives and so on.
> >
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> ------------------------------
>
> Message: 5
> Date: Sat, 18 Aug 2018 09:56:57 +0100
> From: Chris Woolf <***@chriswoolf.co.uk>
> To: ***@music.vt.edu
> Subject: Re: [Sursound] MEMS SNR Specifications
> Message-ID: <f5b56a54-8bbe-5c8e-8066-***@chriswoolf.co.uk>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> I think there is indeed some confusion in this discussion between the
> signal-to-noise ratio of these mics, and dynamic range.
>
> The first is conventionally related to 1Pa/94dB SPL, and one then needs
> to add in a Max SPL figure to get the dynamic range.
>
> We need both bits of information to understand the practicality of any mic.
>
> A noise floor of 24dBA (related to 1Pa) is about par for a small
> personal electret mic. A dynamic range of >115dB is what one would wish
> for in decent professional mics - that would be a noise floor of 15dBA
> and a max SPL of >130dB (with a distortion figure of 3 or 5%).
>
> Chris Woolf (ex editor of Microphone Data)
>
>
> On 18/08/2018 08:41, Bo-Erik Sandholm wrote:
> > According to the document linked to below that relates self noise values
> to
> > real world applications 110 SNR cannot be related to the commonly used
> > reference sound level.
> > 110 dBA SNR would be 16 dB below absolute quiet.
> >
> > If the value 70dBA that I found for the infineon dual membrane MEMS mic
> is
> > related to 1 Pascal, then it's self noise is around 24 dB which is not
> > strictly studio quality.
> > But not really horrible.
> > If it is related to max 10% distortion which is at 135 dBA thats not a
> > realistic comparison value as the result is a self noise of 65 dBA.
> >
> > That would be a noise source not a microphone :-) !
> >
> > So a bit of apples and oranges comparison is going on ??
> >
> >
> >
> http://www.neumann.com/homestudio/en/what-is-self-noise-or-equivalent-noise-level
> >
> > SIGNAL-TO-NOISE RATIO
> > Another way to document the noise performance is to specify the
> > signal-to-noise ratio. But relative to what signal? The reference sound
> > pressure level for noise measurements is 94 dB (which equals a sound
> > pressure of 1 pascal). So you can simply calculate:
> >
> > Signal-to-noise (db-A) = 94 dB ? self-noise (dB-A)
> >
> >
> >
> > The actual signal-to-noise ratio in use, of course, depends on the sound
> > pressure level of your sound source.
> >
> >
> > Bo-Erik
> >
> > On Sat, 18 Aug 2018 01:37 Jack Reynolds, <***@gmail.com>
> wrote:
> >
> >> Are you sure the Ambeo has 110dB SNR?
> >>
> >> Sent from my iPhone
> >>
> >>> On 17 Aug 2018, at 23:56, Paul Hodges <pwh-***@cassland.org>
> wrote:
> >>>
> >>> --On 17 August 2018 14:55 -0700 Ralph Jones <***@comcast.net>
> >>> wrote:
> >>>
> >>>> Some folks posting here have seemed to suggest that this level of
> >>>> noise might possibly be acceptable.
> >>> Well, firstly we don't know the actual specification of the devices
> >>> used by Zylia. And secondly, using an array of nineteen to generate an
> >>> output gives the possibility of significant improvement, because the
> >>> sound source signals are correlated and the noise is uncorrelated.
> >>>
> >>> How this holds up in practice at higher orders and higher frequencies I
> >>> will attempt to judge when I get my hands on the ZM-1 rather than just
> >>> predicting failure in advance (which is not consistent with the reviews
> >>> I've seen heard and read).
> >>>
> >>> Paul
> >>>
> >>> --
> >>> Paul Hodges
> >>>
> >>> _______________________________________________
> >>> Sursound mailing list
> >>> ***@music.vt.edu
> >>> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe
> here,
> >> edit account or options, view archives and so on.
> >> _______________________________________________
> >> Sursound mailing list
> >> ***@music.vt.edu
> >> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> >> edit account or options, view archives and so on.
> >>
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>
> ------------------------------
>
> Message: 6
> Date: Sat, 18 Aug 2018 11:52:59 +0200
> From: Fons Adriaensen <***@linuxaudio.org>
> To: Surround Sound discussion group <***@music.vt.edu>
> Subject: Re: [Sursound] MEMS SNR Specifications
> Message-ID:
> <***@mail1.linuxaudio.cyso.net>
> Content-Type: text/plain; charset=us-ascii
>
> On Sat, Aug 18, 2018 at 09:41:13AM +0200, Bo-Erik Sandholm wrote:
>
> > According to the document linked to below that relates self noise values
> to
> > real world applications 110 SNR cannot be related to the commonly used
> > reference sound level.
> > 110 dBA SNR would be 16 dB below absolute quiet.
>
> Maybe possible with an unexistium membrane and left twisting electrons ...
> :-)
>
> > If the value 70dBA that I found for the infineon dual membrane MEMS mic
> is
> > related to 1 Pascal, then it's self noise is around 24 dB which is not
> > strictly studio quality. But not really horrible.
>
> It's the self noise figure which matters in the end. It simply means
> that if you record a sound with an SPL of say 60 dB (at the mic), the
> S/N ratio would be 60 - 24 = 36 dB. Using a 'pro' mic with a self
> noise of 10 dB the S/N ratio would be 50 dB. In both cases assuming
> the preamp doesn't add a significant amount of noise.
>
> Noise of 'virtual mics' (or ambisonice components) synthesised from
> multiple capsules is not so simple.
>
> If S_i is the signal from the i-th capsule then the beam signal is
> of the form
>
> S_beam = sum (a_i * S_i) i = 1..B
>
> where the a_i are complex gains depending of frequency. Now if the
> a_i are scaled such that the on-axis sensitivity of the beam is the
> same as that for a single capsule, then the noise power in the beam
> signal is the sum of the squares of the a_i:
>
> N_beam = sum (a_i ^ 2)
>
> For an 'omni' pattern this typically results in a significant
> improvement, up to 3dB * log2 (N) in the best case (ommi
> capsules at low and medium frequencies).
>
> For directive patterns, almost anything can happen depending
> on if the capsules are omni or directional, if they are in
> free space or on a solid body, and the order of the pattern.
> The actual noise will not be white which means that traditional
> noise figures (e.g. A-weighted) become more or less useless.
>
> Typically you may see some improvement over the single capsule
> noise level in some small frequency region, and more noise
> in other frequency bands.
>
> For some examples, get hold of the original Eigenmic manual
> which shows noise performance as a function of frequency
> for each of the available patterns. That's the only example
> I know of a manufacturer documenting this, most (including
> Zylia) will hide the truth in lots of blabla.
>
> Ciao,
>
> --
> FA
>
>
>
> ------------------------------
>
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> End of Sursound Digest, Vol 121, Issue 13
> *****************************************
>
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Stefan Schreiber
2018-08-28 13:25:04 UTC
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Citando Florian Grond <***@gmail.com>:

> Hi everyone,
>
>
>
> Regarding the question of which mems the ZM-1 uses, here is some detailed
>
> info I just found:
>
>
> https://www.infineon.com/cms/en/about-infineon/press/market-news/2018/INFPMM201808-078.html
>
>
>
> Best,
>
>
>
> Florian

Adding some technical information:

https://www.infineon.com/cms/en/product/promopages/microphones/#technology-00001

Best,

Stefan
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