Easy calibrated vibration measurements on Mac or iOS

digiducer_04_CE_mediumAlthough Faber Mac and iOS apps have offered excellent sound and vibration analysis tools from the start, the introduction of the Digiducer 333D01 USB Digital Accelerometer makes vibration measurement easier and more portable. When the 333D01 is connected to a Mac, iPhone, or iPad, it will be immediately recognized by our apps and ready for calibrated measurements.

For example, SignalScope Pro will recognize the connected 333D01 as an accelerometer and set the measurement units accordingly. SignalScope Pro will also automatically read calibration information from the 333D01 and establish the appropriate sensitivity so calibrated measurements can be made immediately. This works with both the Mac and iOS versions of SignalScope Pro.

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The 333D01 communicates with Mac OS or iOS via the standard USB Audio Class driver. Connecting to a Mac is as simple as plugging the 333D01’s cable into an available USB port. For iOS, Apple’s Lightning to USB Camera Adapter is required.* When connecting to iOS, no additional power source is required, which makes Faber apps and the 333D01 part of an ultraportable vibration measurement system.

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Auto-calibrated measurements with the 333D01 are supported in Electroacoustics Toolbox, SignalScope and SignalScope Pro for Mac, and in IOScopeSignalScope and SignalScope Pro for iOS.

 

Buy the 333D01 USB Digital Accelerometer

Download Electroacoustics Toolbox (Mac)

Download SignalScope Pro (Mac)

Download IOScope (iOS)

Download SignalScope Pro (iOS)

 

*Older iOS devices may require a 30-pin to USB adapter, such as the one available in Apple’s original iPad Camera Connection Kit.

iOS Audio Hardware: Stereo input via USB

If you’re looking for a way to acquire stereo input signals in apps like SignalScope Pro or IOScope, you’ll be pleased to know that you can connect a USB audio device to your iPhone, iPad, or iPod touch via Apple’s Lightning to USB Camera Adapter. Built-in USB audio support in iOS opens up a vast array of options for getting audio signals into, and out of, your iOS device. (USB audio support on iPhone and iPod touch requires iOS 7 or later.)

Compatibility

The trick is to find a device that conforms to the USB Audio Device Class specification, which essentially means that no special drivers are required when connecting the device to a host, like a Mac or an iPhone. Some device manufacturers clearly state that their product works with iOS and some do not. In general, if you find a USB audio device that does not require special drivers to work with Mac OS, then it will work with iOS as well.

Power

One thing to consider when selecting a USB audio device to connect to your iPhone or iPad is power. Some USB audio devices require an external power source, which means portability will be somewhat limited due to the need to have an A/C power outlet nearby. Other devices support USB bus power, which means they’ll draw their power from the host device (e.g. the iPhone). For portability, this would be the ideal situation since the iPhone and input device could be completely portable and operate for the life of the iPhone’s battery. However, only low-power devices can be directly powered by an iPhone or iPad, which means that a lot of otherwise compatible USB audio devices cannot be connected to iOS without some other source of power. For bus-powered USB devices that require more power, it is possible to maintain some portability with a USB battery power supply and an additional adapter cable.

A Few Examples (portable and inexpensive)

Stereo USB Audio Devices
Behringer UCA202
The UCA202 from Behringer offers very inexpensive and portable stereo input for iOS.

It features:

  • 16-bit/48 kHz sampling
  • 2 inputs and 2 outputs with RCA jacks
  • Headphone output with volume control (1/8″ jack)
  • Low power operation so it can be powered directly by an iPhone or iPad
  • S/PDIF optical digital output
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Behringer UFO202
The Behringer UFO202 is similar to the UCA202. Instead of a digital output, it offers the option to select between line-level and phono preamp input.
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ART USB Dual Pre
Another inexpensive option, which also adds mic preamps with switchable 48V phantom power, is the USB Dual Pre from ART.

It features:

  • 16-bit/48 kHz sampling
  • 2 inputs with XLR / 1/4″ combo jacks for mic preamp or line-level input
  • 2 outputs with 1/4″ jacks
  • Headphone output with volume control
  • Low power operation so it can be powered directly by an iPhone or iPad
  • Switchable 48V phantom power, powered from a 9V battery
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Adapters
Apple Lightning to USB Camera Adapter
This adapter is all that’s needed to connect a compatible USB audio device to an iPhone, iPad or iPod touch with a Lightning connector. As indicated above, if your USB device needs additional power, additional components will be needed. That will be discussed in a separate article.
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Apple iPad Camera Connection Kit
If you have an older iPhone or iPad with a 30-pin dock connector, you can connect a USB audio device with the USB adapter included in this kit. Remember that iOS 7 is required for USB audio on iPhone.
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SoundMeter adds support for iTestMic and iAudioInterface2

SoundMeter 6.3 and SoundMeter Pro 2.3 now officially support the iTestMic and iAudioInterface2 from Studio Six Digital.

With iTestMic, microphone sensitivity will be automatically loaded from calibration information stored in the iTestMic’s internal memory. This calibration information may have been set at the factory, or it may have been set from within an app, such as SoundMeter. In SoundMeter, it is possible to perform a sensitivity calibration without overwriting the calibration values stored in the iTestMic. SoundMeter can also store that information in the iTestMic for calibrated measurements in other apps that support the iTestMic. SoundMeter also supports selecting iTestMic’s high and low input ranges.

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Note: There is currently a bug that sometimes invalidates the calibration information stored within the iTestMic for the High mic input range. This bug affects use of the iTestMic with Studio Six Digital’s own apps, as well.

With iAudioInterface2, SoundMeter can select between mic and line input types, mic and line input gain ranges, and manual volume control options. The volume control knob of the iAudioInterface2 can be assigned to the input gain or the output gain, or it can be disabled entirely to avoid accidentally invalidating the current sensitivity calibration. Also from within the app, Phantom power and digital audio output may each be enabled or disabled. SoundMeter remembers each of these settings for the next time you connect iAudioInterface2 or relaunch the app.

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The new SoundMeter apps also support the Dayton UMM-6 USB measurement microphone. When the UMM-6 is detected, the user will be prompted to enter its serial number, which is typically printed on a label on the UMM-6. If a valid serial number is entered, SoundMeter will automatically download a calibration file from Dayton’s website and set the microphone sensitivity based on the information in the file.

Note: The Dayton UMM-6 must be connected to your iOS device via Apple’s USB camera adapter (either for Lightning or 30-pin dock connector, depending on your device). Sometimes the UMM-6 shows up in iOS as USB PnP Sound Device. If that happens, unplugging the UMM-6 and plugging it back in will generally solve the problem (it may take 2 or 3 tries). When properly connected, “UMM-6” will appear as the input device name in SoundMeter’s toolbar (at the top of the screen).

Download SoundMeter 6.3

Download SoundMeter Pro 2.3

 

iOS 7 Brings USB Audio Support to iPhone and iPod touch

I’m not sure how I missed it, but I discovered this week that USB audio devices can now be used with iPhones that support iOS 7 as well as the 5th generation iPod touch (I have personally confirmed that it works with iPhones as old as the iPhone 4S and the 5G iPod touch–iOS 7 is required in order for this to work). This is great news for anyone looking to perform multi-channel or high-quality audio or acoustic analysis with something smaller than an iPad.

The iPad has supported USB audio input and output, via the iPad Camera Connection Kit, from the beginning. Until the advent of iOS 7, however, this functionality was not supported on iPhone or iPod touch. Now, a whole host of devices, ranging from inexpensive stereo USB audio interfaces to higher end multichannel interfaces, can be used with the iPhone or iPod touch you carry in your pocket. Smaller, simpler USB interfaces will draw their power directly from the iOS device. More sophisticated hardware will require some kind of additional power supply. In any case, it is important to note that the USB audio interface must support the standard USB Audio Class driver (if it works with Core Audio on your Mac, without the need to install special drivers, then it should work with your iPhone).

In order to connect a USB audio interface to an iPhone, either the 30-pin USB adapter of the old iPad Camera Connection Kit or a Lightning to USB adapter is required (depending on whether your iPhone has a 30-pin or Lightning connector on the bottom). The screenshots below demonstrate success with a Behringer UFO-202 connected to a 5th generation iPod touch and a Tascam US-800 connected to an iPhone 5S. The UFO-202 runs completely off of power from the iPod (or iPhone), so it is a completely portable solution. The US-800 requires external power.

 

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Measuring the inexpensive, bus-powered Behringer UFO-202 with SignalScope Pro running on the 5th generation iPod touch.

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Measuring the inexpensive, bus-powered Behringer UFO-202 with SignalScope Pro running on the 5th generation iPod touch.

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Analyzing 6 input channels simultaneously with SignalScope Pro running on the iPhone 5S. The input device is a Tascam US-800 sampling at 96 kHz.

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Analyzing 6 input channels simultaneously with SignalScope Pro running on the iPhone 5S. The input device is a Tascam US-800 sampling at 96 kHz.

 

If you have had any experience connecting USB audio devices to your iPhone or iPod, I would love to hear about it in the comments. What have you found that works? What doesn’t?

 

Download SignalScope Pro from the App Store.

 


Are you looking for a measurement microphone for your iPhone?

Since iOS 6 finally remedied the low frequency roll-off problem of the headset mic input of the iPhone, iPod touch, and iPad, the headset jack has become a suitable option for measurement microphone input. Prior to the release of iOS 6, the only way to connect an external measurement microphone, without sacrificing low-frequency information, was to go through the dock connector. Dock connector devices can still provide higher quality solutions, but working with the headset jack offers a level of portability (i.e. compact size) that cannot be matched when a 30-pin dock connector is involved (we’ll see what comes along to take advantage of the new Lightning connector).

MicW i436

Some time ago, I was made aware of the i436 measurement microphone from MicW. It looked like exactly what was needed to turn any iOS device into a quality sound level meter, or acoustical analysis tool, that you could truly carry around in your pocket. However, it was limited in its utility by that pesky low-end roll-off that plagued earlier versions of iOS. Some developers attempted to perform software correction for the input filters, but when an input signal is driven into the noise floor by the hardware (or firmware), there’s nothing app software can do to restore the lost signal at those lower frequencies. Now that iOS 6 has solved the issue, the i436 has become the attractive measurement microphone solution for iOS that it should have been when it was first introduced.

i436i436

Last weekend, I carried the i436 around the Denver Tech Center Marriott at the Rocky Mountain Audio Fest (RMAF), along with my iPhone 5. The i436 is small enough that it could slip into my pocket and remain there unnoticed or it could stay connected to the iPhone, which was perched in my shirt pocket when it wasn’t in my hand. In short, I was quite pleased to confirm that the i436 does indeed make for a portable measurement solution that you can carry in your pocket all day long.

MicW i436 Noise Measurement

As for quality, the i436 looks and feels like a proper measurement microphone. It was designed to meet the Class 2 standard for sound level meters, which addresses issues like environmental stability in addition to frequency response. The i436 also fits a standard microphone field calibrator, with a 1/4″ adapter, which you would also expect from a measurement microphone. A field calibrator makes microphone sensitivity calibration very easy with measurement software like SoundMeter or SignalScope Pro.

i436 Typical Frequency Responsei436 Typical Polar Pattern

The i436 is available in a package with just the mic, or in a kit. The kit includes a wind screen, extension cable, splitter cable (to connect headphones or an audio cable to the headphone output), a small clip, and an aluminum storage tube that doubles as a holder for the i436 that mounts to the top of a standard microphone stand (very handy).

i436 Single Packagei436 Kit Package

If Class 2 compliance meets your needs, then I highly recommend the MicW i436, especially in the kit. Either option is quite affordable for a quality measurement microphone. If you need a microphone that conforms to the Class 1 standard, then another hardware solution will be necessary.

iPhone 5 compatibility with existing audio input accessories

Since the Lightning to 30-pin Adapter (0.2 meter cable) arrived yesterday, I have had the opportunity to test several audio accessories with the iPhone 5. The results are presented below. Only accessories that worked with the iPhone 4 were tested, since earlier audio input accessories couldn’t be expected to work with the new iPhone (they relied on the analog input pins that were not supported on 4th generation iOS devices).

30-pin audio input accessory compatibility

Accessory iPhone 5 iPhone 4/4S
Apogee Jam Yes Yes
Fostex AR-4i Yes (1) Yes
Line 6 Mobile In Yes Yes
Sonoma Wire Works GuitarJack 2 Yes Yes
Tascam iU2 No (2) Yes
  1. There were a few times that I couldn’t get the iPhone 5 to recognize the Fostex AR-4i, but once it did, the AR-4i worked well. Sometimes, the iPhone would give the same message as that for the Tascam iU2 (below).
  2. When connecting the iU2 without USB power, the iPhone 5 wouldn’t recognize it. When USB power was supplied to the iU2, the iPhone would present a message which said, “The connected USB device is not supported.”

iPhone 5 audio consistent with iPhone 4S

Today, I had the opportunity to begin testing the audio input characteristics of the new iPhone 5. As seen in the plots, below, the headset input frequency response matches that of the iPhone 4S, which was presented in the previous post. The behavior of the built-in microphone also seems to match that of the iPhone 4S, suggesting that Apple kept the audio input path essentially unchanged in the new device.

One current limitation of the iPhone 5 is that existing dock connector accessories for audio input (and output) are not compatible, due to the iPhone’s new Lightning connector. As soon as Apple’s new Lightning to 30-pin adapter arrives, we’ll be able to see if it enables existing audio accessories to work with the new iPhone. Until then, the headset input and built-in microphone will have to suffice for iPhone 5 users. Fortunately, iOS 6, which comes installed on the iPhone 5, allows us to bypass automatic gain control and the high pass filter that plagued the headset input and built-in mic in earlier versions of iOS.

iPhone 5 Headset Leq iOS 6

iPhone 5 Headset Leq iOS 6 Fine Scale

GuitarJack Rocks 3rd Gen iPhone and iPod touch

While the GuitarJack, from Sonoma Wire Works, was obviously designed with music recording in mind, it also works well as an I/O interface for test and measurement apps, like SignalScope Pro and IOScope. The GuitarJack, and the iAudioInterface from Studio Six Digital, are the only two iPod accessories I’m aware of that properly support both line level input and output via the 30-pin dock connector of iPhone and iPod touch devices. (The Alesis ProTrack supports line-level input and output, but not both simultaneously.)

GuitarJack and iPod touch 3G

GuitarJack In Brief

  • Simultaneous stereo line-level input and output
  • Compatible with 2nd and 3rd generation iPhone and iPod touch devices (Sonoma recommends using Airplane mode when using GuitarJack with an iPhone. Also, I had success using GuitarJack with the 1st generation iPhone and the 1st generation iPod touch, although I noticed that the GuitarJack’s low frequency rolloff was worse with those devices.)
  • High-impedance input available
  • Software-programmable input gain (Currently, gain settings are only accessible from within Sonoma’s FourTrack iPhone app.)
  • Reasonably flat frequency response over the audio band
  • Built to last (Its case is metal instead of flimsy plastic, like so many other iPod accessories.)

GuitarJack Frequency Response

The following plots of GuitarJack’s frequency response were produced with IOScope running on an iPod touch 3G. It’s important to note that these measurements include the response of both the output and input circuitry.

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1/4

1/4

1/8

1/8

The frequency response magnitude is down by 2.6 dB at 20 Hz, relative to 1 kHz, when working with the 1/8″ input or the 1/4″ input in Lo-Z mode. As can be seen in the plots, the Hi-Z mode produces more low-frequency rolloff than the Lo-Z mode (its response is down by about 3 dB at 40 Hz). The GuitarJack rolls off the low end more than I would like, but it’s response is still pretty good for an iPod accessory.

GuitarJack is not compatible with iPhone 4, iPad, or iPod touch 4G. Fortunately, Sonoma appears to be working on a solution for the new iOS devices with model 2.

GuitarJack is available now for $199.

iPod touch 4 limited like iPhone 4

While built-in cameras and a microphone are exciting additions to the newest iPod touch, the same I/O limitations that plague the iPhone 4 as an audio/acoustics analyzer platform remain. In other words, the existing audio inputs on the 4th generation iPod touch suffer from significant low-frequency roll-off, just as the other iPhone and iPod touch models do. Also, existing analog line-level input accessories that worked with earlier iPod touch and iPhone devices (before the iPhone 4) are not compatible with the latest iPod touch.

In spite of the present limitations, however, I’m sure it’s only a matter of time before suitable input options become available for the latest and greatest iOS devices…

iPhone 4 Audio and Frequency Response Limitations

The iPad’s lack of line level audio input support via the dock connector certainly raised the question of what would be in store for the iPhone 4. Now that I have my hands on the new iPhone, I thought I would go ahead and report on the state of audio I/O on the new device.

Here’s what seems pretty clear, based on my initial tests of the iPhone 4:

  • The iPhone 4 does not accept standard iPod accessories with line level input
  • Unfortunately, the new iPhone doesn’t work with the USB connector of the iPad camera connection kit, either, so there really isn’t a two-channel audio input option at the present time.
  • The frequency response of the iPhone 4’s headset mic input is virtually identical to that of the iPhone 3GS.
  • The built-in microphone’s frequency response also closely matches that of the 3GS.

iPhone 4 Headset Input Frequency Response

iPhone 4 Built-in Microphone Frequency Response

It really is unfortunate that there is currently no way to get stereo signals into the new iPhone 4, although I’m confident that it’s only a matter of time before an acceptable solution presents itself. Beyond this glaring limitation, the iPhone 4 is essentially the same as the iPhone 3GS (and iPad) in terms of its audio performance. It will be interesting to see, though, what new possibilities open up with the A4 processor, the increased memory, and the high-resolution display (which is quite amazing, by the way).

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