Mobile sound Recorder

January 25, 2017
Wireless CCTV Camera Module
Mic on phoneWe’ve sung the praises of the portable audio recording device before, and for good reason. They’re small, portable, dedicated boxes that allow you to quickly and easily perform audio recording, monitoring and delivery of world-class audio for your video projects. But it’s possible to outfit your mobile device with those same features and more, turning them into audio recording devices. Your mobile device is already small, portable and battery powered, so that’s covered. It contains a small computer, a display and audio jacks and, with the addition of a few extras, will do the job of its purpose-designed cousins.

Audio recording apps are all over the place, for iPhone, iPad and Android and you’ll have no trouble experimenting with several variations. Obviously, some are better than others. In fact, the really tricky part is getting the audio off of your smartphone. That means an audio interface or adapter cable(s). That’s where things get sticky.

Audio in iWorld

Apple has it nailed. They design and manufacture their iPhone and iPad among other devices. They also developed the operating system and control all the apps available to you in the iTunes store. This translates to a generally seamless integration of hardware, software and peripherals, with the possible exception of the new Thunderbolt connector. Some iPods, iPhones and iPads have the same connector, which made it possible for third parties to develop add-ons that enhance capabilities and extend their function. And many audio manufacturers did just that. Some are basic docks or audio interfaces that provide additional inputs and outputs while others are full-blown mixing consoles that operate in software. All of them turn your iPhone or iPad into an audio recorder.

If you prefer a simpler approach, consider a splitter cable for the audio jack. If you’ve ever examined the earbud plug for your mobile device, you may have noticed four connections rather than the three connections common with stereo headphones. The multi conductor connector allows for the left and right channel earbuds along with a mono microphone connection. This is called a TRRS connector for Tip, Ring, Ring, Sleeve. StarTech.com, and others, make adapters specifically for the purpose of piping audio into your mobile device. To use the splitter, plug it into the audio jack of your mobile device, plug headphones into the headphone jack and a microphone into the mic jack. Remember that this is a mic input and requires mic level audio signals if you’re feeding it with an outboard mixer or other audio devices. Adjust your output levels accordingly. Finally, launch your audio recording app and do a quick audio level test.

Close up of “Share Via” page on audio software interfaceDon’t rely on the built-in microphone or even the included microphone preamp in your mobile device.

Audio for Android

The Android operating system has grown exponentially since its release just a few years ago. Since then, more than 900 million devices have been activated, meaning you almost certainly know someone who owns one of these mobile devices. But, unlike Apple’s iron-fisted ecosystem, Android is more like the Wild West. With 15 major manufacturers and no less than nine versions of the operating system in circulation, it’s fair to assume there is far less compatibility than with Apple’s platform.

First, there is no standard dock or I/O connector on Android devices, so you’re limited to the audio jack for input and monitoring. Fortunately, the splitter cable we mentioned earlier works equally well on iOS and Android. Second, not every Android device has a TRRS connector to turn it into an audio recorder. In fact, several tablets - including Google’s Nexus 7, contain only a standard headphone jack. Android phones are usually a safe bet, but check the specifications for your particular make and model to be sure. Third, due to multiple operating system versions and hardware platforms, not every audio app will work on every device. The Google Play Store simplifies this with a notification of compatibility for your specific device(s) prior to installation.

Best Practices

Regardless of the hardware or software you choose, there are several things that will help you capture and deliver the best possible recordings from your audio recording devices. Don’t rely on the built-in microphone or even the included microphone preamp in your mobile device. While some are pretty good, an external preamp will be much better if you can use one.

Make sure your audio recorder app allows live monitoring of the audio signal, with headphones and meters if possible. Audio is audio regardless of your recording path and good monitoring is essential for good recordings.

Look for an audio recorder app that provides an audio sensitivity adjustment to help match your audio signal to the device. Alternatively, use an external preamp or mixer to do the matching. As a last resort, consider using microphone placement to compensate for audio levels. Many mobile devices have hardwired Automatic Gain Control or AGC circuits. There may be no getting around it, so do a couple of test recordings and make adjustments for the best compromised settings.

Record in the highest possible quality. Many recording apps store their files in MP3 or .3ga format. These are lossy, compressed formats. While they will work in a pinch, you’ll lose quite a bit of quality. Whenever possible, record to WAV or AIFF files. They’ll take up more space, but the audio quality won’t suffer.

Be aware of the available capacity of your memory card. It’s easy to fill mobile devices with hundreds of Instagram pictures, multiple copies of Angry Birds and Candy Crush, so make sure there’s enough room for your recordings. If possible, insert a large microSD card and instruct your recording app to place its files there.

Many audio recording apps contain editing and signal processing options. Usually, you want to do as much of this as possible in post-production. However, there may be times when a quick in-app edit is just the thing. Simple editing trim points are common in many apps and the next steps are normalize functions, along with basic fade-in and fade-out.

When it’s time to move your audio recordings to the video edit suite, there are multiple options. You can always plug in a USB cable to transfer recordings, and iPhone users should be familiar with moving files via iTunes. If you’re recording to a separate memory card, you can pop it out and slide it into a card reader for transfer. These are the standard methods, but don’t forget — you’re using a connected device. You can add files to your Google Drive account, Dropbox, Evernote and even email. It’s usually just a couple of taps away and much easier than pulling the back off your phone to access the memory card.
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