Post processing noise reduction help needed... (1 Viewer)

[fmhill]

Howdy all,

I'm looking for information on post processing noise reduction/removal software and at present I use Audacity.

I'm mostly interested in bird sounds, songs, and calls and I find that while Audacity has a lot of great editing tools, to my way of thinking, the noise removal function is not one of them. It is a powerful tool, it will really knock the noise down at but at the expense of modifying all but the very strongest bird/wildlife sounds. A real tin can alley if you over do it...

Maybe someone has some information that would help a beginner set up the Audacity noise removal functions? I'm using the default values and reducing the dB setting from 24 to 12 dB which seems to help on low level noise.

Let me draw you a verbal map, the mid and upper Cape Cod, MA USA area where I live has a lot of nice wildlife spots, however few are very large or very quiet being bordered by roads and housing areas. There are heavily traveled highways going out both sides of the Cape with heavily used secondary roads networking the towns and
villages. There are many boat harbors along the coast and boats are loud and very noisy, add to that the Cape has quite a few airports along it, I have one airport 2 1/2
miles north of me, another 4 miles north east of me and a Military/USGS field another 8 miles to the west.

I'm fortunate that my home borders a 15 acre treefarm which is loaded with wildlife. However there are two major secondary roads intersecting only 100 feet from the
north west corner of the treefarm, one of these roads along the west edge of the farm is the main road into the village and beaches, the other road travels along the north edge of the Treefarm and is the highway bypass going between two heavily populated villages... We have two Audubon
wildlife areas close to me, one borders the road running between villages and Rt.28 on the far side, the other is nestled between the road exiting Rt. 6 and Rt.6 which is the main highway out the Cape. Both of these roads are
heavy traffic all the time... Talk about frustration!

Point of this is, about the only hope of making decent sounding files of what we hear and can record in this area requires heavy post processing, primarily noise removal...

So, Dear Friends, what does one do besides sell out and move far, far away?

I'm hoping there is some software package that you know about that will help...

Thanks for your help and advise...

 

[HarryJ]

noise

Hi,
Here are some quick thoughts about noise. It can be a real trouble. The first and foremost thing in reducing noise is to plan and select carefully the recording site and recording time. If you can get to a inherently quiet place then good. My favorite site is some 60-100km (40-60mi) from home. If travelling is not a possibility then you should pay attention to the most quiet moments in your neighbourhood. In daylight hours the quietest times in a week tend to be Sunday (and Saturday) dawns and mornings. Mornings are often quite calm too, which is helpful. I have also noticed that within a year there are a dozen of so very quiet mornings, those when people linger at home. For example, christmas morning (people are digesting christmas dinner - which was served here on Christmas eve), or the 1st of May (when all drunks have passed out, and all sober people are still sleeping, and virtually the whole country is shut down). Even if your roads don't get silent, they tend to be quieter around certain times and those moments can be precious. You need to find out when those times are in your neighbourhood.

Getting close to the bird without disturbuing it increases the signal to noise as you can reduce the gain (of the noise too). If you have a shotgun/parabolic microphone then you shoud consider the positioning of your mic. If your back is towards the noise and you hold the mic in front of you it helps a bit in reducing the noise as you create a noise shadow. A fence or a wall behind you could also be very helpful.

Noise, or unwanted sound, comes in so many different forms. If your noise is say from a closeby aggregate featuring a fixed pitch sound with a constant amplitude (showing as repeating pattern in the oscillogram data or a straight line in the sonogram) then most of its contribution can be removed. If your noise source is a single car or a boat, where the pitch and the intensity vary with time, then really there is no means in removing it. A more uniform noise created by a many distant vehicles or by the microphone/recorder background is in principle reducable by a bit, but inherently this kind of random noise is difficult to remove without affecting the true signal. (It can be done to a certain extent using wavelets, but I don't know if these are used.)

I use audacity to reduce noise by 6 or 12 dB at most - its is reasonably good for that. Note that if you reduce the noise by 10dB, you are in principle reducing it by a factor of 100 or moving your highway 10 times further away. In the software you can also cut off all the sounds say below 200Hz, or 400Hz if you are after high pitch sounds. Do this after you have applied possible noise reduction softwares, and keep this in moderation.

Wishing you quiet moments

HarryJ

 

[fmhill]

Hi HarryJ,

Thanks for the reply and information. Unfortunately traveling very far just to record sounds of birds and other wildlife is not very practical for me due to other obligations which keep me close to home. Besides, the birds and wildlife here are what interest me most.

The Cape is quite unique in its geographic location making it a major stopping over point for birds to rest and refuel on their spring and fall migration up and down the Atlantic flyway coastal migration route.

BTW, I do practice many of the methods you suggest, I use a ME66/K6 microphone and try to keep my back to the roads as much as possible and that helps quite a bit. Unfortunately, when I turn my back to the roads I'm pointed at a narrow strip of old growth woods with a large school complex beyond it with huge air conditioning plants on the roofs of the buildings and afternoons having very noisy games on a number of playing fields. This area is also directly under the primary air traffic rout from Boston to Newark NJ for the airlines and at lower altitudes for the turbo-prop and small jet commuter planes flying from the Cape Cod Hyannis Airport (located 4 miles north east of me) going to Martha's Vineyard and New York City area.

During the day, the Tree farm is active with heavy equipment moving trees in and out, it is primarily a tree moving service with about 15 pieces of heavy equipment as well as sales of Nursery stock and supplies so I keep my activities limited to after hours when I have free run of the place. The treefarm works 6 days a week and I plan my walks for Sundays and after 6:00 PM in the afternoon when it is quiet and the birds are active.

Using the Glame highpass filter function in Audacity set to 400 hz helps a lot and I keep the low cut-off enabled in both the microphone and the recorder which also helps.

In my experimenting I have found that setting the noise reduction parameters to 12dB, frequency smoothing to 400 and attack/delay to 0.08 sec works quite well but I'm wondering if anyone has a better solution.

There are times that the noise level here is extremely high and not all bird sounds can be recorded at optimum level. I have a recording at the moment I've been working on to extract a very high pitched unique sound to ID and unfortunately, it becomes distorted no matter what I do. Between the aircraft noise and the construction equipment noise I may have to give up on it. Regrettably, its the only recording I've been able to make of this one particular sound...

I have heard of a software, "iZotope RX - Complete Audio Restoration" however have heard nothing about it from users using it for bird and wildlife sounds. I was hoping by posting here, someone would have a recommendation for it or something similar or possibly something more suitable for what I'm trying to do...

Thank you very much for your reply.

 

[ermine]

it's probably not what you want to hear but filtering out wideband noise is not usually possible without distorting your wanted signal.

OTOH man-made noise varies very strongly with time. On early summer mornings you can often beat a lot of the noise by getting up around 4 am

 

[fmhill]

it's probably not what you want to hear but filtering out wideband noise is not usually possible without distorting your wanted signal.

OTOH man-made noise varies very strongly with time. On early summer mornings you can often beat a lot of the noise by getting up around 4 am

I grant you 4:00 AM is probably the quietest time here but regrettably its usually the time the large heavy diesel trucks are on the roads delivering produce to the markets. Also, being a major tourist area, early morning is when the working folks are getting to their jobs beating the tourists rising and getting on the roads.

This time of year the Cape runs around the clock it seems...