Noise Filtering

I have a large number of data files containing values for acoustic and vibration data from machinery. I am trying to look for distinguishing features in particular groups of files (covering certain dates) but there is a lot of random noise contained within the signals so this is proving difficult. I am plotting time domain and f domain of the individual files and the f domain does show up some peaks. However if I try to average the FFT (which I believe is a valid signal processing technique for a set of similar signals), the peaks just get lost in the noise. Therefore, I'm looking for a way to remove the noise across all the frequencies I'm measuring (0-25kHz). I'm a beginner at this, so if it sounds like I'm on completely the wrong track, feel free to
set me straight!

Your signal is basically composed of two types of signals that are:
1 - The deterministic ones, like tones or DC
2 - The non-deterministic ones, like true noise
When you take a single snap-shot and perform an FFT, it can sometimes be difficult to determine whether a "peak" is caused by a deterministic tone or happens to be a noise component, especially if your expected tones are of the same order of level as your expected noise components. A single FFT measurement of a pure white noise signal typically results in a variation in level (as function of frequency) of more than 10 dB, so you may see peaks that may be confusing.
That is where averaging becomes handy. So if you are averaging correctly (RMS averaging), and your "peak" disappears, it most likely
means that ... it wasn't a tone.
If you want to detect tones that are "almost" embedded in the noise, you have different options, including:
1 - Use RMS averaging and see if that uncovers your tones
2 - If not, try to perform your FFT on a longer time record. You will achieve 3 dB improvement in selectivity every time you double your record length.
3 - (This may not be applicable in your case). If you have a way of triggering on a "copy" of the signal you are looking for (like if you want to detect 50-60 Hz power hum, you could trig on the Main power), you can then use Vector averaging. This will more or less average your tone signal correctly while removing un-correlated noise the more you average.

Similar Messages

WHITE NOISE FILTERING

Hi,
Please any one resend this file by converting to labview 9th version
White noise filtering and Lms attached are in labview 10th version
I am unable to open 10th version, I have the 9th version
Attachments:
WHITE NOISE FILTERING_BT (1).vi ‏158 KB
LMS (1).vi ‏11 KB

Try posting in the Downconvert thread.
They can change the version of the VI for you.
Cory K

Noise filteration

Hi
I’m using NI6040E Daq to measure frictional torque and speed of the drive shaft. The sampling rate i'm using is 1000 s/s. The problems I am facing are:
The speed pick-up generates a 5V signal at every revolution of shaft. The shaft runs from 100 to 5000 rpm and I am struggling to get right VI in LabVIEW to show me real time speed of shaft.
The torque signal is superimposed by a 50Hz noise at all speeds (think this might be from the mains). And higher frequency noises as the speed approach 5000 rpm. Which will be the right VI to filter these noises from the signal?
Thanks

For (1) it sounds like you need to just use the counter on your DAQ board.
For (2) while you can filter the stuff out in software, you are far better off taking care of this in hardware. See, for example:
http://zone.ni.com/devzone/cda/ph/p/id/154
http://zone.ni.com/devzone/cda/tut/p/id/3344
http://zone.ni.com/wv/app/doc/p/id/wv-364
http://zone.ni.com/devzone/cda/pub/p/id/262

Ecg noise filtering

hello everubody
first of all i want make a ECG signal in VI page but i can't
and after that i want add a noise to this signal and denoise that later with adaptive filter
can you help me . i can't make a ECG signal . i downloaded the ((simulated-ecg)) files and copy in user.lib but i cant use them
i see these errors
please help me step by step until i make this project
thanks a lot
Attachments:
ecg1.jpg ‏147 KB
ecg2.png ‏132 KB

Hi Hami45,
The Biomedical Toolkit needs to be installed and registered for the VIs within it to work properly. You will be able to use it in evaluation mode for a time if you have not purchased it yet.
Josh B
Applications Engineer
National Instruments

Noise filters-eliminating annoying Crow(yes the Birds!) sounds

I took some footage in Sri Lanka (tiny Island South East Asia) - the problem is outdoors there are so many Crows! they are Everywhere,...like an Alfred Hitchcock movie! So a lot of these interviews I did have these annoy dull "Kaaw! Kaaw!" sounds continuously in the bits. Anyway to get rid of these sounds? Maybe a custom filter, or may be just a normal filter? I am only interested in the Primary Subject's (interviewee) voice so background sounds are not important to me either.

Yes, I understand your concern. Just trying to offer a creative solution to the challenge you'll face, trying to remove the squawking of the crows.
If none of your video from Sri Lanka contains crows flying about, (for context) it may be a challenge to effectively incorporate the idea. Since I don't know what you have for footage, I can only suggest possibilities.
Any chance your footage shows a crow flying off behind the subject? If so, go outside and shoot a crow flying of in the sky and cut to that...again just setting up a reference to your viewer why they hear crows in the intv. If course, it'd be great if you had mountains and/or tropical flora in the background...
If your budget warrants, maybe you can acquire some stock footage of crows pecking at food that Aid Refugees are clamoring for...
K

How do PS CS3 Noise Reduction Filters compare with dedicated third-party plug-ins?

Am I missing something by not installing a dedicated Noise Reduction application into my PS CS3? Can Neat Image, Noise Ninja, Noiseware Pro, etc. do something that the PS CS3 Noise Filters can't do? Do these third-party aplications do it better?
Since I like flashless photography, and I generally carry with me small-sensor compacts when I travel, I'm frequently confronted with the problem of digital noise. I've always wondered how the third-party noise reduction applications perform in comparison with the Photoshop Noise Filters. I hope someone in this Forum has been able to acquire direct experience on this topic and will be kind enough to share this experience with us.
Kindest Regards,
Conrad

Conrad,
ACR 4.3 has better NR (noise reduction) than previous versions and can handle NR in most normal situations. However, available light photography with a small pixel sensor may require more NR and the specialized plugins such as Noise Ninja, NeatImage, and NoiseWare Pro can do a better job. I have all three and they do an excellent job, but I currently use NoiseWare most of the time.
Here is a demonstration of NoiseWare vs ACR NR, using 100% crops of an image taken with the Nikon D200, 1/320 sec at f/2.8. The image is reasonably sharp at normal viewing conditions, but has quite a lot of luminance noise. It was rendered with ACR and the settings were exposure +0.85, brightness +60. One thing you learn early in this type of shooting is to expose to the right to reduce noise, but this may conflict with stopping action and reducing camera shake. More exposure would have helped this image, and one should try to avoid exposures requiring this amount of positive exposure adjustment.
The results are shown below, followed by some discussion. Other comments are welcome. Color noise is not prominent in this image and I left color NR at its default.
ACR, No sharpening, no NR
ACR, Luminance NR 53, no sharpening
ACR, No NR, No sharpening, NoiseWare default, no sharpening
Noise reduction and sharpening are antagonistic processes. It is important that NR is applied before sharpening--you don't want to sharpen noise. Following NR there is an inevitable loss of detail, and some sharpening is necessary to restore the detail, but this also brings back the noise. One can use masks and blend if sliders in Photoshop in both NR and sharpening to mitigate some of these effects, and Bruce Fraser discusses the details in his excellent book on sharpening.
If you use an add on such as NoiseWare, you should turn off luminance sharpening in ACR. In doing so, you lose all those nifty sharpening features that have recently been added to ACR. I leave color NR at the default. It has a minimal effect on detail.
In adjusting the NR in ACR at 100% viewing, I estimated that a luminance setting of +53 was optimal. Beyond that, blotchy artifacts appear in the image.
For NoiseWarePro, I used the default settings with no sharpening. The NR effect is dramatic, but detail is lost and some sharpening is needed. This could be applied in NoiseWare or in Photoshop, perhaps with a plugin such as PhotoKit Sharpener. Personally, I have found that PK does not work well with this type of image because it bring back noise and produces artifacts.
In all of these examples, sharpening is needed following the NR. One could try to use surface masks to keep sharpening in Photoshop with the unsharp mask away from the edges. However, I find it is difficult to get a good surface mask, and I don't take the trouble.
For now, I use the sharpening built into NoiseWare. I don't know how it works internally, but it does have a slider for detail protection, and you can play with this to get the best result. It would be best to have the robust NR of the add ons built into ACR much like NoiseNinja is built into Bibble Pro. However, this is an ACR forum and I would expect that ACR is the preferred raw converter of those who frequent this forum.
After expending this much effort on the post, I hope to get some helpful feedback.

Noise filter Illustrator CS4

I nned to apply a noise filter in Illustrator CS4. The filters seem to have gone and only effects are there. I know I can use the noise filter in Phoshop, but would like to keep it ion a vector environment. Are there any downloads for noise filters available? Where woul;d I find them?
Many thanks
otti

Larry G. Schneider wrote:
If you want the same result as the old filter, just use Expand Appearance after using the Effect. The new way offers the chance to make changes in the future instead of locking in the changes.
Larry...
Where's the 'Noise' filter?

Lot of noise from laptop audio output

I'm getting a lot of noise from the audio output of my Macbook Pro (early 2008) OS 10.8.5 when I connect an external firewire 800 drive that uses a power cord. I get more of the same noise when I connect an external video monitor. The noise is a digital hashy and whiney sound that modulates sometimes as what on the screen changes. If I use my Focusrite Scarlett interface the noise is amplified to the point that I can't work. The noise starts when the drive's power cord is plugged in. If I work off a pocket USB drive there is no noise. This is my work around for now. I'm using a power strip that has noise filtering. I have 2 different studios and I get the same noise in both. I've done a lot of trouble shooting and have narrowed the problem down to connecting a drive with a power cord to the computer. I have tried different drives too with the same result. Is there any hope of fixing this?

Can't say I've ever had any noise when starting the unit up over optical - if your DAC is designed for stereo only then it may be causing noise by attempting to play the 5.1 startup video's audio bitstream which is dolby digital encoded not stereo.

Film Noise/Grain is killing me, please help...filter or other ideas?

Hi all, thanks for your help!
I have some footage and I shot it with a XL1. I don't know why but there's a ton of static what I would call grain. However, no grain filters or noise filters seem to get rid of it. What's the difference between grain and noise anyway?
Does anyone have suggestions for how I might get rid the the grain. Motion Blur works but when my interviewee talks it looks ridiculous so I can't use that.
Thanks,
Paul

I had to fix this kind of problem once. The only way I came up with was with Shake, but someone posted some plugins for FCP that might do the trick...
Check out this thread:
http://discussions.apple.com/thread.jspa?messageID=1067315&#1067315
Patrick

Filtering an analog signal

i am taking voltage readings as analog signals and was wondering do i need to filter the signals that come from the daq assistant. i tried smoothing the signals but this did not match the values that i should be getting is there any other filter signal that would be suitable or do i need to filter my analog signals at all as they are reasonably accurate as they are but was wondering would filtering improve the accuracy that much

Hey Guys!
AC-class signals, such as vibration, often require antialiasing filters. Like standard noise filters, the antialiasing filter is lowpass; however, it requires a very steep cutoff rate, so it almost completely removes all signal frequencies that are higher than the input bandwidth of the device. If the signals were not removed, they would erroneously appear as signals within the input bandwidth of the device.
But not all NI DAQ devices will have antialiasing filters built in. Devices designed specifically for AC-class signal measurement – the NI 455x, NI 445x, and NI 447x dynamic signal acquisition (DSA) devices, the NI 61xx simultaneous-sampling multifunction I/O devices, and the SCXI-1141 module have built-in antialiasing filters.
Ultimately, anti-aliasing must be carried out in hardware. But the time you have digitised your signal, it is too late to remove aliased signals. However, general noise removal filters can be implimented post-acquisition (i.e. in software).
Have you looked at the Filter Expres VI? Or, if that is not flexible enough, have a look at the low level filter vis, which can been found under the signal processing pallette. They are available in either array manipulation or point-by-point flavours.
You may not require them, but for advanced filtering, you might want to have a look at the "sound and vibration" toolkit.
http://sine.ni.com/nips/cds/view/p/lang/en/nid/12050
Best wishes,
Rich R
Applications Engineer
National Instruments UK & Ireland

Is ALAC Filtering Audio?

I'm currently in the process of importing a rather sizable library of CDs into iTunes and have opted for ALAC as the file format of choice.
However, when evaluating the sound quality of the ALAC files, there definitely seems to be a lacking transparency between the source CD tracks and the ALAC files. More specifically the ALAC files sound as if they have gone through some sort of noise filtering similar to Dolby NR or MPX. The best way I can describe the difference is a loss of transparency in the ALAC files at the higher frequency range compared to the original source CDs.
I should note that all of my evaluations have been done solely on my PowerBook using iTunes 7.0.1... thereby ruling out different D/A converters as a possible cause to this perceived lacking transparency.
I would like to know if anyone with knowledge of ALAC can give some insight as to whether what I'm experiencing is a phenomenon intrinsic to lossless compression or something more isolated to just Apple's lossless encoder. With the overwhelming abundance of material on lossy audio formats, I've found that finding good reference documentation on lossless audio has been something of a struggle.
I would greatly appreciate more insight on the technical fundamentals that go into lossless compression.

I'm 99.9999% confident that it is just your imagination.
Apple Lossless, like all other lossless codecs, uses a technique called linear prediction: http://en.wikipedia.org/wiki/Linear_prediction
More to the point, Apple Lossless, like any other lossless codec, can be encoded and then decoded again. When you compare the two results, they are bit-perfect.

Film restoration project, need filters

Does anybody have any recommendations for filter plug-ins for FCP for a film restoration project I'm doing? I had about 1600' of old family 8mm movies scanned to DV and I'm editing them together. As expected they are more than rough around the edges. They could stand some noise filtering and some heavy color correction (over exposed, under exposed, you name it) I've looked at a few of the plug in vendors (Joe's Filters, CHV Plugins, Boris) but I don't have any experience with any of them. I'd like to avoid buying the wrong product as much as possible.

Hello there,
as I regularly need to handle (ancient and recent ) S8 footage my general advice would have been to color correct while scanning (with a scanner like the german-engineered MWA FlashScan8 which has a primary color correction built into the hardware).
Anyway, as you are obviously already beyond this step:
FCPs built-in color correction toolkit (Color Corrector 3-way) should be absolutely sufficient to achieve the results you may want. Hence the built-in moniker, it comes free with FCP
For stuff like noise and dirt I would recommend the Too Much Too Soon plugin set.
I contains a pretty good noise reduction plugin and a hair removal plugin.
http://www.mattias.nu/plugins/
It's free too, so there should be no (price) concerns whatsoever.
For really heavy-duty pre-processing (e.g. actual film restauration) there are some pricey options available.
RedGiant has the "FilmFix" product available ($800 or so?). This is an AfterEffects plugin that more or less can (semi-)automatically correct all problems associated with age-old film stock: flickering, noise, vignette, hair, scratches, grain etc.
http://www.redgiantsoftware.com/filmfix.html
From british company TheFoundy comes "Furnace" for Shake.
The algorithms in this product are more or less the same as in FilmFix.
As the restauration functionality is only a part of the package it's even more expensive ($4000?).
http://www.thefoundry.co.uk/pkg_plugins.aspx?ui=44213E51-76C0-4926-9D5D-3A805944 9900
These two options above are actually able to really clean up the footage.
From an aesthetic standpoint I usually prefer to keep as much of the "authenticity" of the S8 footage as possible, fixing only the major technical glitches.
To do so, the two option I described first will do just fine, IMHO.
Best regards, Oliver

I'd like to know how I can acquire a waveform on a loop and do a circular buffer with this waveforms I will acquire, cause I want to reduce the noise.

I'm using trigger for this data acquisition.

deco,
If you really want a circular buffer, how much data do you want it to hold? One acquisition? Two? Three? Once this is decided, you will need to create the waveform and then continuously strip the old data out and place the new data in. This will add a bit of overhead to your VI.
There are also software noise filters in LabVIEW that you can use to reduce the noise in your signal.
Lastly, if there is a lot of noise, you may want to consider an SCXI system which will filter out most of the noise as the data is being acquired.
Randy Hoskin
Applications Engineer
National Instruments
http://www.ni.com/ask

Removing noise in optical motion capture data

Hello to you.
I am building my own optical motion capture system. In
relation to this I have coded a modified K-means clustering
algorithm in LINGO, which can be used for removing image noise in
the captured image data. Noise is in this case regarded as being
sparse groups of pixels (e.g they do not belong to a marker as
these are represented as compact pixel groups).
In order to evaluate the performance of my algorithm I need
to compare it with some other noise filtering solution. Does anyone
know if there is any suitable such LINGO code available? Possibly
Mean or Median filters…
I hope for positive replies:)

Jan Carlo wrote:
> Hello to you.
>
> I am currently trying to remove noise in image sequences
containing
> motion capture data. As a part of this project I am
clustering pixels
> into groups and want to remove pixel groups with less
than 4 members
> as these groups are regarded as noise.
>
> The problem is that when I have a nested list with e.g 3
sub
> lists/clusters (as indicated below) and I use a repeat
loop to remove
> the sub lists with less than 4 pixel coordinates, but my
code does
> not seem me to do this correctly (There are three sub
lists where 2
> of these should be removed, but only 1 of these 2 are
deleted while I
> am unable to remove the last one).
>
> Does anyone have any suggestions on how I can modify the
current code
> so that it does the job correctly?
>
The problem is that you're deleting things from the list
you're looking at
and things get moved towards the start, thus skipping an
iteration you
wanted to examine. If you start at the end, you won't get
that problem.
on test
clusters = [ [point(477, 453), point(477, 459), point(477,
460),
point(478, 454), point(478, 456)], [], [point(462,
405),point(462,
405),point(462, 405)]]
nMin = 4
nClusters=count(clusters)
repeat with i = nClusters down to 1
if clusters [ i ].count < nMin then
clusters.deleteAt(i)
end if
end repeat
put clusters
end test
Andrew

Noise through firewire audio device 27" iMac

I am using ProTools 9 with the MBox Pro audio interface (8in - 8out). I am experiencing an intolerable noise floor that I have narrowed down to coming from the firewire port itself off my new iMac i7 27' with 8G RAM with the 2G graphics. I have not even received my Apple Care package yet; that is how new we are talking!!
Note that I tested against my MacBook Pro which is impressively quiet (all references to "quiet & noise" have to do with the firewire output), and exhibits none of these symptoms: The iMac powers up/boots and a few clicks can be heard while it locks in with the MBox. There is an almost immediate faint high-pitched whine that can be heard, very faint unless you were to turn the volume up, but something like the sound you would hear on a video taken from an airplane. Once ProTools opens, or any program that has some meat on the bones, the whine boosts up even louder. This time it is an unacceptable "not good for business" noise. If you scroll the dock, or move the arrow across the dock, it sounds like white noise you would hear as if thumbing through stations on an AM radio.... and truthfully, because it is coming from my now questionable investment, way worse than an AM radio. This "dirt" coming from my firewire port is so strong, even after turning the Mbox off, this noise is bleeding right on through to my mixer anyway - even the AM radio noise when scrolling!
If you let the computer sit at a modest volume, once the screen saver kicks in, every picture that comes up has it's own noise, sort of like you're hearing voltage spikes from a utility transformer... so I am wondering if this could be a bad graphics card since it seems closely related to what changes on the screen? Anyone who is having these sound issues, please share. Last note: None of these conditions changed with relocation of my monitor speakers, new cords, screen resolution adjustment, or monitor brightness adjustments.

" So make no mistake, this is an issue that should be taken into consideration by Apple to address and initiate corrections in the electronics/power supply/materials or perhaps the internal design.
My follow-up post was an explanation of how I resolved the issue, but for the price, most who experience this will feel should have been resolved before their iMac was even assembled."
James230,
I have to say I do not agree with this comment.
Apple can not be made accountable for electrical systems that are not up to today's standards and codes and causing noise on your power line.
You state in your second post that the power in your area as no Earth ground and that the ground prong of your house's electrical system is grounded on conduit.
In the end grounding to conduit is the same as grounding to earth since the water intake for your house IS in the ground so all pipes connected to it are acting as a ground to earth.
The problem is that there is so much stuff connected to the water pipes, like a water heater, kitchen sink, washing machine, etc. that can create interferences, and make it a very noisy ground.
"like the battery back-up, the AC connected to it is simply charging the battery but the actual power running the laptop is through the battery.."
Not true.
The UPS solution you used is the right thing to do, but not because of the battery.
The battery in a UPS is NOT powering your equipment when you have normal electrical power on. It will only be used when the power goes out.
Same thing goes for your laptop, the battery will only be used when it is not getting power from a wall outlet.
The electricity is powering your power supply which is powering your laptop and charging your battery as needed.
Remove the battery from your laptop and it will still run from power from a wall outlet.
You are getting a cleaner ground because most decent UPS devices available today are equipped with power conditioning and noise filtering circuits that will eliminate most of the noise created by inadequate grounding.
Also note that using a ground lift like you first suggested is not only dangerous for your equipment but could also be seen as "abnormal conditions" that could be used as a reason by any equipment maker to void the warranty on their equipment if a electrical problem was found to be the cause of damages.
They could say: "Sorry, your equipment was not properly grounded, so we are not covering these repairs."

Noise Filtering

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