Noise Reduction Waves

[Marieta Reeks]

Hi all, I'm currently helping a friend out editing sound for his short film and there is a couple of scenes shot on and around a beach, we are struggling as one of the actresses speaks quite quietly and is conflicting with the sound of the rough sea and waves, just wondering if anyone knows a fixable solution to either lower the background noise of the sea, effects in audition or premiere that might be helpful or how to raise her voice without raising the full track so it doesn't conflict as much, ADR isn't an option really so it's got to be something we can fix In the edit if we can.

There is no easy solution here. Waves are very difficult because they are broad spectrum and fluctuating. Some Izotope/de-noise work and automated eq will do something, but ADR is probably your best bet.

This is tricky, just had the same situation recently. Noise reduction might not get you very far, particularly with a very quiet voice. You want to retain as many frequencies in the voice as possible. The one benefit of the fluctuating nature of the waves is that if you have access to alternate takes and shots, you could be able to find different quiet spots in each one and piece them all together.

ADR it. You'll spend less time doing it and you'll need to process the crap out of it to try and save it. Steve hit it on the head. the sound fluctuates, (it's not a steady state sound which can be more easily be fingerprinted by BNR programs) . the amount of processing you'll wind up doing will make the audio sound terrible. Re-record it and drop in a beach SFX. That way you can control the ocean.

A better philosophy on location if you're surrounded by background noise is to wait for a break (or the end of the scene), then take the actors as far away as possible from the noise -- like the ocean -- and record a series of wild lines, just in the hope that the sound editor might be able to use those instead of the live dialogue.

On Lost, I was often impressed how the crew would get the wide shot actually in the location, but then on the close-ups, they'd pull the actors back on the beach and shoot the scene in such a way that you weren't aware they were no longer standing in the ocean, and they'd point the mics towards the actors and away from the waves. The sound was often amazingly good, given their challenges. (Overhead jet planes were also occasional issues.)

The sooner a wild line is done the better. And in this day and age, 57640 takes happen of a shot. Digital domain... However, if there is a problem with take 1 of the 57640 takes, and IF it stays that way over all takes, obviously a wild take needs to ameliorate this problem.

I remember a film i did in 2005 - period piece (1857 AD) being shot in the most inconveniencing locations for sound. NYC based Producer was a moroness who came up to me on Day 1 of the shoot and did not want me to wire up actors because 'this is not TV! you need to use boom mics!'

Noise-cancelling technology cannot wholly isolate sound due to the air trapped between your audio device and eardrum. However, the air is essential for you to hear music. Suppose you removed the trapped air; the net effect is silence, no matter what volume your music is on. Why? There would be no medium for the sound to travel from the audio device to your eardrum.

Noise-cancelling audio devices use a built-in microphone to analyse the ambient sound waves around you and generate the opposite sound waves to reduce surrounding sound. Noise-cancelling devices have a built-in microphone which produces the opposite reversed sound waves to neutralise surrounding noise. Noise cancellation works best when the ambient sound around you is constant and around the low to medium pitch range.

Now consider the fluctuating pitch levels when you speak. The sudden changes in pitch occur too frequently and make it difficult for any noise-cancelling audio device to analyse and process these differences. Therefore, you hear some noises whilst others are cancelled out.

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Detected squeezing level as a function of measured antisqueezing measured at 5.2 kHz. The blue and red traces represent fits to the respective data points. The fitting procedure fits a common parameter for optical efficiency, η. The two solid traces represent estimates of the detectable squeezing level if a factor of 2 reduction of optical loss (green) and phase noise (yellow) could be realized. The dashed black trace is a factor of 2 improvement in both. This shows that we are still primarily limited by optical loss.

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Modern active noise control is generally achieved through the use of analog circuits or digital signal processing. Adaptive algorithms are designed to analyze the waveform of the background aural or nonaural noise, then based on the specific algorithm generate a signal that will either phase shift or invert the polarity of the original signal. This inverted signal (in antiphase) is then amplified and a transducer creates a sound wave directly proportional to the amplitude of the original waveform, creating destructive interference. This effectively reduces the volume of the perceivable noise.

A noise-cancellation speaker may be co-located with the sound source to be attenuated. In this case, it must have the same audio power level as the source of the unwanted sound in order to cancel the noise. Alternatively, the transducer emitting the cancellation signal may be located at the location where sound attenuation is wanted (e.g. the user's ear). This requires a much lower power level for cancellation but is effective only for a single user. Noise cancellation at other locations is more difficult as the three-dimensional wavefronts of the unwanted sound and the cancellation signal could match and create alternating zones of constructive and destructive interference, reducing noise in some spots while doubling noise in others. In small enclosed spaces (e.g. the passenger compartment of a car) global noise reduction can be achieved via multiple speakers and feedback microphones, and measurement of the modal responses of the enclosure.

Applications can be "1-dimensional" or 3-dimensional, depending on the type of zone to protect. Periodic sounds, even complex ones, are easier to cancel than random sounds due to the repetition in the waveform.

Protection of a "1-dimension zone" is easier and requires only one or two microphones and speakers to be effective. Several commercial applications have been successful: noise-cancelling headphones, active mufflers, anti-snoring devices, vocal or center channel extraction for karaoke machines, and the control of noise in air conditioning ducts. The term "1-dimension" refers to a simple pistonic relationship between the noise and the active speaker (mechanical noise reduction) or between the active speaker and the listener (headphones).

Protection of a 3-dimension zone requires many microphones and speakers, making it more expensive. Noise reduction is more easily achieved with a single listener remaining stationary but if there are multiple listeners or if the single listener turns their head or moves throughout the space then the noise reduction challenge is made much more difficult. High-frequency waves are difficult to reduce in three dimensions due to their relatively short audio wavelength in air. The wavelength in air of sinusoidal noise at approximately 800 Hz is double the distance of the average person's left ear to the right ear;[1] such a noise coming directly from the front will be easily reduced by an active system but coming from the side will tend to cancel at one ear while being reinforced at the other, making the noise louder, not softer.[a] High-frequency sounds above 1000 Hz tend to cancel and reinforce unpredictably from many directions. In sum, the most effective noise reduction in three-dimensional space involves low-frequency sounds. Commercial applications of 3-D noise reduction include the protection of aircraft cabins and car interiors, but in these situations, protection is mainly limited to the cancellation of repetitive (or periodic) noise such as engine-, propeller- or rotor-induced noise. This is because an engine's cyclic nature makes analysis and noise cancellation easier to apply.

Modern mobile phones use a multi-microphone design to cancel out ambient noise from the speech signal. Sound is captured from the microphone(s) furthest from the mouth [noise signal(s)] and from the one closest to the mouth [desired signal]. The signals are processed to cancel the noise from the desired signal, producing improved voice sound quality.[citation needed]

In some cases, noise can be controlled by employing active vibration control. This approach is appropriate when the vibration of a structure produces unwanted noise by coupling the vibration into the surrounding air or water.

Noise control is an active or passive means of reducing sound emissions, often for personal comfort, environmental considerations, or legal compliance. Active noise control is sound reduction using a power source. Passive noise control is sound reduction by noise-isolating materials such as insulation, sound-absorbing tiles, or a muffler rather than a power source.

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