Those chosen ones with golden ears don’t obviously need any audio spectrum or frequency analysers, but for a rusty-eared guy like me an RTA running on my smartphone is handy. When hunting down feedback frequencies it helps to have a pocket-sized analyser with you. For that you don’t even need a measurement microphone; the built-in microphone is usually enough.
I have tried several free RTA apps on iPhone and the ultimate best of them is Etani RTA. This app, made by a Japanese company that manufactures audio analysing tools, is simple but looks and feels professional. It has a normal spectrum analyser with the maximum resolution of 1/6 octaves. The peak values are drawn as a line on top of the bars. If desired the minimum values can be shown too.
For more accurate analysis one can use a cursor, but it’s restricted to 1/6 octaves and doesn’t snap on transients as you would expect.
It’s also possible to calibrate the analyser, but I didn’t really understand how that works, and the manufacturer hasn’t yet managed to come out with the manual! I ordered the manual using a web form opening from the app, so let’s see. With the free version the analysis period is limited to 15 seconds. That’s usually enough for most basic uses, although a bit inconvenient. In addition it’s possible to save one results and analyse it in a form.
The pro version costs over 50 euros and it’s supposed to have more sophisticated data features. You will also get rid of the 15 second time limit, but otherwise I don’t think that the additional features justify the high price.
In the hunt of feedback frequencies a waterfall spectrograph would be useful, but it seems that you don’t find one in these free apps. In payable apps a spectrograph can be found at least in AudioTools by Studio Six Digital (16 euros). However it seems that the waterfall view works only with the iPad version. By the way, AudioTools is made in collaboration with Rationa Acoustics, the company behind the Smaart analysing software.
Anyway, it seems that Etani RTA is a very decent free analyser that provides joy in many situations.
I’ve also tried a couple of other apps. Of these RTA Lite is a very simple analyser without any additional features. The resolution is 1/3 octaves.
This is also made by Studio Six Digital. The same red bars are familiar from the other software by the company. One example is JL Audio Tools, which features not only an RTA but a sound pressure meter, several calculators for impedances, ohms, etc and a phase meter.
iAnalyzer Lite represents the other end of the spectrum. It is a space-age pocket analyser with a 3D histogram. It’s so fancy that it’s hard to know what to do with it. At least for me it felt very difficult to use it with iPhones’s small screen. Maybe iAnalyzer is designed for iPad and other tablets with a screen big enough use fit two fingers to turn the forest of bars around. According to the AppStore the full version (16 euros) has tons of additional features, so this must be a good app for someone with a very analytic lifestyle.