Soundscape Channel

[Casio Bauman]

Howsanctuary species use sound, and how species and habitats may be affected by sound, is an important area of study as the amount of underwater noise in our coastal oceans continues to increase. Under the guidance of NOAA's Ocean Noise Strategy Roadmap, the sanctuary is dedicated to better understanding underwater sound and has been monitoring the sanctuary soundscape since 2017 using stationary recorders. Sanctuary partners have been monitoring sound in and around the sanctuary for over two decades. Combined, the sanctuary and partners are characterizing the soundscape in both shallow and deep water listening stations across the entire sanctuary. Each year, a NOAA Teacher-at-Sea, many students, and several interns contribute to the sanctuary's sound monitoring research.

Passive acoustics is a non-invasive way to remotely collect sound data across large geographic regions and periods of time that can inform a number of ecological investigations. NOAA and the National Park Service maintain 12 deep water Noise Reference Stations (NRS) across protected areas and areas of interest nationally. The NRS station in Channel Islands National Marine Sanctuary has been recording ambient sound at about 1,000 meters (3,380 feet) south of Santa Cruz Island since 2014. Since deep water listening stations operated by sanctuary partners have been in place for several years, in 2017 the sanctuary initiated shallow water stations in collaboration with the U.S. Navy, NOAA Southwest Fisheries Science Center, and others. This SanctSound monitoring network aims to characterize baseline sound levels, intensities, and variation across habitats and time. Each of the listening locations have been carefully selected to better understand sound sources of interest, such as vessels. Some of the stationary sound recorders are paired with acoustic telemetry receivers to describe how species like fish use sound during certain times of the year and/or for specific reproductive, migratory, or social behaviors. National marine sanctuaries are working to develop trackable sound metrics for condition reporting, as well as education and outreach products and interactive learning platforms.

Paradigm award-winning sound quality! It's a giant sonic step above anything available at the big box stores. Paradigm engineering delivers four beautifully designed 4" composite cone woofers that serve up deliciously deep bass. Our own Digital Signal Processing platform makes sure every note of that bass is clean and musical. Tailor the listening experience with switchable EQ modes to suit placement on a wall or flat surface. Action packed movies or multichannel music? With Dolby Digital encoded material, turn on the Dedicated Movie Mode with Paradigm Virtual Surround for a breathtaking surround experience (full details on this later). Switch to Music Mode for 2-channel listening. Bluetooth capability with aptX coding for high quality audio streaming. Charge Bluetooth devices from another room while continuing playback in the same room. A subwoofer's not necessary, but one can be added (sold separately), a transmitter is built in and a wireless sub receiver is included.

In systems without dedicated surround or rear speakers, much of the wonder and magic of surround sound is lost since there are no physical speakers to deliver it. Carefully mixed by recording engineers in the studio, this precious information sits neglected and unheard in front left and right speakers. Paradigm Virtual Surround. developed by Paradigm engineers, ensures that none of that surround magic is lost. Humans have the ability to hear sound in three dimensions. Through sophisticated mathematical algorithms that capitalize on this ability, Paradigm Virtual Surround processing gathers all the neglected surround sound information in a central sweet spot, then reflows it back into front left and right channels, sending it out into the room in a way that creates the auditory illusion of sound swirling around us. An auditory 'illusion' perhaps, but to our ears this experience is very very real, lifting the Soundscape experience to a realm that is spacious, authentic, immersive and magically engaging.

So I will be doing lots of field recording in Asia for the next few months. I've got a sennheiser me66 for mono spot fx, which is linked into a zoom h4n via the sound devices mm-1 pre-amp (did not want to be using the h4n's pre's). So I think I'm all good there.

My issue is with ambience. I'm just starting out in this field (this is my first rig) and I've got a big name in major motion picture sound to impress. I know I won't be doing much impressing with a zoom device, but I don't have the money/don't want to take anything too expensive around less-safe parts of Asia.

So...do I record ambience 2-channel stereo on my h4n or 4-channel on my h2? I'm thinking 4-channel would be better, but I just got the h4n and don't know how much better or not the onboard mics are than the h2. I would be going for local walla and various nature ambience.

Any other advice is more than welcome too, this is my first time doing all of this so it's a bit daunting knowing I'm going to go back home to Los Angeles after this and try to impress people who have been doing this for twice my lifetime.

I'm not that personally familiar with the recording quality of the H4N vs. the H2, but I would say this: while four channel ambience recordings can be useful, I know far more people who prefer to build their own surround (or the occassional quad for television) ambiences. You have more flexibility and control that way. Chances are good that if you record a quad ambience, and find material that is distracting or you don't like in one of the channels, you're going to break up that group and, in the very least, shift that channel...breaking up the strict quad interaction to anyways. You may replace that channel entirely.

I'd suggest you focus on recording clean, interesting, stereo ambiences...especially considering your rig. You'll be able to respond to the recording environment more easily that way, and you'll probably get a larger quantity of useable material. Remember, if you really want a quad type sound, you can always spin 180 degrees and do a second recording facing the other direction. It won't be true quad, but you'll at least have that second perspective from the location.

I agree with Shaun's comment that stereo recordings are more useful for constructing quad ambiences, in most cases. However, in my opinion the joy of recording is more than just being able to use your recordings for work. I personally love doing quad recordings, just for archival purposes and listening back at a later stage. I might never directly use my quad recordings in a project (more likely I fold them down to stereo or ditch 2 of the channels altogether), but listening back to a nice surround recording of a place that I've visited often gives me more satisfaction than listening to music.

One thing I'm usually quite conscious of is the size and look - I find that the H2 is way more discrete than the h4n, so it's a lot easier to gather stuff without attracting too much attention. Sounds silly, but if you're travelling round "less safe" parts of SE Asia, this might be something to bear in mind!

As Shaun mentions, I would focus on two tracks for ambiences. I think it's way more important to have interesting ambiences that are unique or hard to get or truly bespoke to a location than great sounding ambiences, obviously try anyway to get awesome sounds but don't not record something cause you think it's not perfect. Let the sound designers/editors build up the soundscape. Your sound will pro ably be one layer out of many.

It is important to understand that the way sound travels is very much dependent on the conditions of the ocean. The sound speed minimum at roughly 1000 meter depth in mid-latitudes creates a sound channel that lets sound travel long distances in the ocean.

Sound is refracted just as light is. Refraction occurs not only when light moves from water to air, but whenever the speed of light changes. Similarly, a sound wave traveling through the ocean is bent whenever it encounters changes in the speed of sound. Since sound speed changes with changes in temperature, salinity, and pressure, a sound wave will refract as it moves through the ocean.

There is a minimum in sound speed at a depth of roughly 1000 m in mid-latitudes. Sound speed near the surface decreases with increasing depth due to decreasing temperature. The sound speed at the surface is fast because the ocean is warmed by the sun heating the upper layers of the ocean. As the depth increases, the water temperature gets colder and colder until it reaches a nearly constant value of about 2C for depths below roughly 1000 m. Where temperature is nearly constant, the pressure of the water has the largest effect on sound speed. Because pressure increases with depth, sound speed increases with depth. Salinity has a much smaller effect on sound speed than temperature or pressure at most locations in the ocean. This is because the effect of salinity on sound speed is small and salinity changes in the open ocean are also small.

In the deep ocean at mid-latitudes, the slowest sound speed occurs at a depth of about 800 to 1000 meters. This is called the sound speed minimum. The sound speed minimum creates a sound channel in which sound waves can travel long distances. Sound is focused in the sound channel because the sound waves are continually bent, or refracted, towards the region of lower sound speed. Sound that travels upward from a source at the sound speed minimum is bent back towards the minimum. Similarly, sound that travels down from the source is bent back up toward the minimum.

The following figure has two parts. On the left is a plot of sound speed as a function of depth. The sound speed minimum at a depth of 1000 meters is called the deep sound channel or, more historically, the SOFAR channel. SOFAR stands for SOund Fixing And Ranging. On the right are the paths followed by sound waves as they travel away from the source. These waves are continually refracted toward the sound speed minimum.

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