Notes from the Test Bench
By Bruce Hofer, Chairman & Co-Founder, Audio Precision
Audio Precision recently attended the AES 2012 convention in San Francisco, EUHA in Frankfurt (targeted for hearing instrument manufacturers), and Electronica in Munich—all within a period of just 3 weeks! Notwithstanding the obvious logistical challenges and travel demands upon our staff, we are absolutely ecstatic with the results. I was able to attend AES and Electronica, and I can personally report a very high level of interest in our products and a generally positive outlook for the audio industry. We met many new potential customers and had a number of great technical conversations.
Electronica was particularly noteworthy because of its size and breadth of exhibitors. This year, the show was spread over 14 halls, which I would estimate to be at least 2–3 times the total floor space of the already huge CES and NAB trade shows in the US. Audio Precision was located in Hall A1 which was devoted exclusively to test and measurement equipment of all imaginable types. Indeed, I counted no fewer than 20 different manufacturers of oscilloscopes and DMMs from around the world exhibiting in this hall along with more esoteric equipment like high power measuring devices, temperature and humidity controllers, flying probe board testers, etc.
I was particularly struck by recent advances in LED technology for home lighting (an entire hall was devoted to just display and lighting devices). The technology is now available to replace the incandescent lamp and fluorescent devices, although it is still somewhat expensive. Several of the exhibits included demonstrations of various shaped LED lamps with and without their covers. The raw LED chips were absolutely blinding in intensity when energized!
I mention LED technology because Munich experienced a major power blackout during the morning of the third day of the show—apparently the worst outage Munich has experienced in over 20 years. There was no official explanation, but many locals were speculating that the power grid within Germany is now overloaded since they have switched off their nuclear power generating facilities.
The impact of the outage was severe. The entire city ground to a halt as all of the subways and trains (the U-bahn and S-bahn networks) stopped working, some for up to 2 hours. Exhibitors and visitors found it very difficult to get to Electronica which was located on the eastern outskirts of Munich. I personally had to use the display backlight of my laptop to shave that morning!
But, back to audio. In this month’s issue you can read about some of the newest additions to our APx500 software as well as some tips on accessing APx functionality and properties with LabVIEW.
As always, I welcome your feedback.
Special: Electronica 2012 – Munich, Germany
Electronica was another wonderful show. As was the case in 2008 and 2010, we saw some extremely interesting applications in which customers from outside the audio world were interested in the superb low noise and 1 million point, 1 MHz FFTs of AP analyzers. It’s also good to see that European production lines are firing up with many new projects, especially given the economic woes on the continent. We were well represented with four sales engineers from Admess, Admess's owner Günter Adam, and AP's Tom Williams, Bruce Hofer, Dave Schmoldt and James Kelly.
Output: APx500 v3.2 Sneak Peak
It seems like only last month we were talking about APx500 v3.1. Well, it was only last month, but AP engineers have been staying up later that usual and have another set of enhancements almost ready to go. Perhaps it's the rainy weather here in Oregon.
Here is a bit of what you will see in APx500 v3.2:
Support for Bluetooth® mSBC wide band speech
The Bluetooth option for APx audio analyzers will now support the popular mSBC wide band speech codec. With a sample rate of 16 kHz (instead of 8 kHz), wide band speech offers a significant improvement in speech quality and is being incorporated into many new Bluetooth voice products.
Note: if you have an older APx Bluetooth option module, it may require a firmware update for mSBC support. Contact your AP representative for more information.
More (and more) PDM decimation ratios
Many of you have requested a larger selection of decimation ratios for PDM in order to accommodate the wide range of clock frequencies found in smartphones, tables, and other devices. In addition to current ratios, APx500 v3.2 now supports ratios of 1, 3.125, 4, 6.25, 8, 8.33, 10.67, 12.5, 16, 16.67, 18.75, 21.33, 24, and 25 on it's input. All PDM ratios may be set in the GUI or via the API.
Pascal/dBSPL calibration for acoustic measurements
If you work with acoustic transducers, then very often you wish to calibrate tools and express results in acoustic units of measurement: dbSPL or Pascals. This new feature of APx allows you to set microphone calibration for each channel independently in dbSPL or Pascals so that multiple or different mics can be used simultaneously, expressing results in these same calibrated acoustic units.
Custom derived results
Sometimes you may need to perform operations upon APx results in order to do comparisons, change units, or make calculations that are derived from multiple sets of results. This is now possible within APx with Custom Derived Results, a feature that allows you to take external data and combine it with current measurements within a sequence for display directly in APx500.
Sound Advice: Accessing APx .NET Properties with LabVIEW
The APx LabVIEW Driver is a collection of Virtual Instruments (VIs) aimed at providing LabVIEW users the ability to access most of the functionality available in the APx500 Application Programming Interface (API) using high level, LabVIEW-typical subVIs, with a minimum number of programming steps. While the APx LabVIEW driver includes VIs for every APx500 measurement, there are some less frequently used advanced settings that are not built into the supplied LabVIEW drivers. An example are those settings accessed through the Advanced Settings dialog in each measurement.
Nevertheless, any setting in the APx UI can be read or set in LabVIEW by constructing a VI that directly accesses the associated .NET Methods and Properties in the APx API. To see all the methods and properties available, open the API Browser from the APx500 folder in the Windows Start menu.
The following example will step through constructing such a VI. This VI will independently set the generator level for each channel in the Level and Gain measurement. In the APx500 UI, this functionality is provided by clicking the Advanced Settings button in the Settings Panel of the Level and Gain measurement.
Fig 1 (larger version)
Place an APx Open VI. Then, right click on the APx500 Reference Out terminal of the VI, select Create > Property for AudioPrecision.API.APx500 Class, and choose LevelAndGain. Note that you can also perform this operation on the APx500 Reference Out terminal of any existing APx LabVIEW driver VI.
Fig 2 (larger version)
From the LevelAndGain property, right click and create a new Generator property for the ILevelAndGainMeasurement class.
Fig 3 (larger version)
Connect the new Generator property, and then in a similar way add an AnalogLevels property to the ILevelAndGainGenerator class. From the AnalogLevels property, create a SetValue method and connect it.
Fig 4 (larger version)
Add an additional SetValue method for channel 2 and complete the VI as shown above.
You can see additional examples by simply opening up any VI in the APx LabVIEW driver and opening its sub VIs until you see the .NET methods and classes. In this way, you can also modify any of the provided VIs to access to additional functionality.
Test Results: AP News
Just a reminder that audio test is everywhere, if you have eyes to see...
© 2012 Audio Precision, Inc.