The H2 in-built mics are OK for Instamatic recording and the AT822 has good stereo field where the H2 mics do not at the expense of noise for which, in most urban and similar environments, is perceptibly lost thanks to my brain helping out. A plus side on the external mic is the low cut for windy situations and the fact that the mic units in their assemblies are much more tolerant to wind than the H2 in-builts.

So, as a workable set up for Instamatic sound recording, a little bulkier and a lot less stealthy but overall, worth the effort. I think that if Sony managed to get their act together on Hi-MD usability I’d still be using my units regularly and so would many others.

I have a few microphones and combined with different recorders, don’t sound consistent. Issues being all the elements that make up the chain between the noise itself and the recorded sound. That’s going to include the noise source, background noise (that the brain often filters out), the microphone, the microphone cable, the recorder and any compression artefacts added to the recording if you are not using an uncompressed file format.

I have also been trying to unravel the technical details to understand why. So I used a little bit of Google and quite a bit of reading. In the end I didn’t really get to grips with it, so I will carry on knowing how my gear works in which situations (which is probably the best approach). Here are a couple of snippets of interesting details/science/etc.

I found this as a good start point, a rule of thumb for microphones.

Max SPL = The point where the mic distorts, or clips the waveform. [More=better]
Self noise = The amount of noise the mic creates all on it’s own. (i.e. hiss). [Less=better]
Dynamic range = The range between self noise and Max SPL. [More=better]
Signal to Noise ratio = The range between self noise and a reference signal. [More=better]

Reference

• http://homerecording.com/bbs/showthread.php?t=276820

So a good start.

But then you don’t always get this data from all microphone specifications. So this explains on how to fill in the gaps.

Some mics may only provide a specification for signal to noise ratio instead of self-noise. Higher numbers are better on this one. Fortunately you can figure out the self-noise from this if they provide enough info. Typically microphone signal to noise ratio is related to a reference acoustic level of 1 Pascal (Pascal is a unit of pressure and relates to “Sound Pressure” [SPL]). A typical rating might be 70 dB, 1 Pa @ 1 kHz. 1 Pascal is equivalent to 94 dB SPL. So, for a S/N ratio of 70 dB you can assume the self-noise to be 24 dB. There are a variety of testing methods, standard, and units of measurement that can come in to play to further muddy the waters, but you will find that most reputable microphone manufacturers will generally give you enough information in a standard enough format to make a comparison.

Reference

• http://www.sweetwater.com/expert-center/techtips/d–01/06/2004

So what does this mean then? For nature recording, getting close to the subject with any thing will give a good result. Further away from the subject will require more recording gain, therefore potentially more recording hiss.

What I usually do is record at relatively low levels quieter sounds and then use an audio file editor (usually Audacity) to amplify. when I can hear hiss being introduced I usually then filter out with a low pass filter. If the recording is used on its own you can hear the difference, but if mixed in with something else, rarely heard.

For mechanical sounds, things are a bit easier. High pass and low pass filters can be used to cut our unwanted sound and also enhance wanted sound. Using a spectrum analyser is sometimes useful for finding out these frequencies. Additionally to high/low pass filtering, EQ can be used to address specific noises on specific frequency bands.

I won’t dwell on the technical differences as these are quite easy to google but briefly, both are single point stereo microphones with capsules in X-Y configuration.

Power

Both mics are battery powered (NT4 9V or phantom, AT822 1.5V) so work well with things like minidisc and a zoom H2. This means that the NT4 works well with almost everything but the AT822 is better with plug-in power type devices.

Weight

The NT4 weighs about double (I would guess but have not weighed them on scales) that of the AT822. This could important for when you end up standing like a statue to capture a sound you weren’t expecting.

Costs

The NT4 also costs about double what an AT822 does. My at822 was £120 via ebay and the NT4 was £240 via competitive high street store.

Sounds

The AT822 I would say is better at soundscapes (wide sounds with lots of variety/range), in that it picks up and handles off axis sound better than the NT4, but then the NT4 is more accurate and directional. The NT4 also picks up sound from behind the MIC array – something that I don’t think the AT822 does. One important difference for the casual user is the AT822 is better at handling windnoise and comes with a lowcut/filter. The better performance in a slight breeze is I think, down to the fact that the mic capsules are have a protection screen build around them and that the mic capsules themselves (I think) are smaller. The NT4 will distort in a very slight breeze, whereas the AT822 handles well with the low pass filter (has proved itself at the top of a hill in moderate winds).