Tech Notes


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Technote 132: Fractional Octave Analysis with APx Audio Analyzers (417.0 kB)

TechNote 132 discusses fractional octave analysis and introduces Audio Precision's octave analysis plugin for use with APx500 Series audio analyzers. This downloadable file is only the technote PDF.

Please use the link below to download a zip file containing the plugin and technote.




Technote 131: Measuring AGC with APx Audio Analyzers (442.0 kB)

TechNote 131 discusses the fundamentals of automatic gain control (AGC), how to measure AGC in hearing aids and other audio devices using the APx attack-and-release measurement plugin, and how to make other, related performance measurements. This downloadable file is only the technote PDF.

Please use the link below to download a zip file containing the plugin and technote.




Technote 130: Measuring Audio-Video Sync with APx Audio Analyzers (448.0 kB)

TechNote 130 discusses how to make A/V sync measurements using an APx500 Series audio analyzer and Audio Precision's A/V sync plugin. This downloadable file is only the technote PDF.

Please use the link below to download a zip file containing the plugin and technote.




Technote 120: Smartphone Audio Test App 2.1 for Android 4-6 (2.08 MB)

This technote describes and explains the use of the APx Smartphone app for Android-based devices, including:

  • How to install the necessary software on the smartphone or tablet device under test (DUT)
  • How to use the Smartphone app on the DUT
  • Which APx projects to use for testing the various signal paths

NOTE: this file is the technote only.

Audio Precision's Smartphone audio test app for Android allows for full testing of audio pathways, including Bluetooth HFP and A2DP, without initiating a call over the network.




Technote 129: Production Test with APx Audio Analyzers (1.1 MB)

This Technote examines the automated test capabilities built into the APx500 measurement software, with emphasis on features recently added in release v4.2 to support production test of electro-acoustic devices. TN129 also provides a practical example, specifically the configuration of APx for production test of loudspeakers, and includes discussion of "golden units" (reference devices), input equalization, multiple sequences in a single project, and Production Test mode.




Technote 128: Speech Transmission Index Measurement with APx Audio Analyzers (460.10 KB)

This TechNote discusses STI measurement, including the different methods identified in IEC 60268-16, a brief comparison of STI versus PESQ and/or POLQA perceptual audio testing, and finally a full discussion of STIPA method-based measurements using an APx500 Series audio analyzer and Audio Precision's STI measurement plug-in.




Technote 126: Jitter Testing of PDM Devices (1.21 MB)

This Technote is intended for those involved in design and test of devices with Pulse Density Modulation (PDM) interfaces. It requires an Audio Precision APx analyzer with the APX-PDM option module (model 228), APX-AMC Advanced Master Clock, and APx500 software version 4.2 or later.




Technote 125: Using APx to Test Dante-enabled Devices (1.77 MB)

Enabling high-channel count, high-quality audio transport via Ethernet, the Dante protocol is being designed into a growing number of pro-audio products and systems. However, testing Dante-enabled devices can present some unique challenges. Our latest technote delves into this application and walks through two example test scenarios using APx500 Series audio analyzers.




Technote 124: Measuring ADCs and DACs with the APx555 (2.30 MB)

This Technote explains how to use the APx555 high performance audio analyzer to perform measurements on Analog-to-Digital Converters (A-to-D or ADC) and Digital-to-Analog Converters (D-to-A or DAC). The measurements include those defined in AES17-1998 (r.2009) “AES standard method for digital audio engineering – Measurement of digital audio equipment” published by the Audio Engineering Society and typical measurements specified in data sheets for converter products and converter IC components.

Now provided as a .zip file including APx500 project files.




Technote 127: Leveled Acoustic Output (1.14 MB)

Technote 127: Leveled Acoustic Output, PDF only. To test acoustic input devices like microphones and hearing aids, users typically want to stimulate the device under test (DUT) with an acoustic signal at a specified sound pressure level (SPL). In addition, to measure the frequency response of acoustic devices, it is desirable to create a sound field that has the same sound pressure level over a wide range of frequencies. This is sometimes referred to as "€œleveled acoustic output."




Technote 123: Measuring Bluetooth A2DP Profile Audio Quality (825.30 KB)

The A2DP Bluetooth® profile is used for high quality music transmission, employing a variety of supported codecs that include MPEG-1, MPEG-2, MPEG-4, AAC, ATRAC, aptX and aptX Low Latency. This technote illustrates how the APx Bluetooth option is used to control and monitor codec selection, measure latency, and test all essential audio parameters such as frequency response and THD+N for Bluetooth-enabled music playback devices.




Technote 121: Perceptual Audio Testing (1.21 MB)

Technote 121 describes the PESQ and POLQA Perceptual Audio test models, how they are implemented in APx, and when each is appropriate to use.




Technote 121: Perceptual Audio Testing Supplemental Files (3.49 MB)

This ZIP file contains Technote 121 and supplemental material regarding PESQ and POLQA from OPTICOM GmbH.




Technote 117: Measuring PDM Microphones and Inputs with APx (2.03 MB)

This Technote has a short review of how PDM works, describe relevant audio tests, looks at the APx PCM module, and conclude with hands-on testing of a PDM MEMS microphone and a PDM microphone input.




Technote 118: Measuring Jitter with J-Test (740.97 KB)

Describes how to use J-test, a special digital test signal which stimulates worse-case jitter over an AES3 or SPDIF digital audio connection. It allows jitter to be measured on an analog output after D/A conversion.




Technote 115: Measuring Microphone Preamplifier Noise (1.36 MB)

Making noise measurements of microphone preamplifiers (and other high-gain circuits) involves special techniques that differ from those used to measure low-gain devices. This technote explains the theory as well as how to make these measurements.




Technote 116: Testing Smartphones and Tablets (3.53 MB)

Smartphones and tablets provide many ways to route audio. This technote shows you how to make connections and test the sound quality for a variety of these signal paths. Where possible, we will use file-based test signals and recordings to measure the quality of signal paths so that we are not measuring the impairments of multiple paths simultaneously.

Includes the accompanying APx project file. The associated APx Smartphone and Tablet Video Test Files and APx Smartphone and Tablet Audio Test Files may be downloaded separately.




Technote 114: Measuring Phantom Power (1.12 MB)

Describes how to test microphone preamplifier phantom power, with and without simultaneous audio. You may instead download the APx Phantom Power Measurement Project, which runs the tests (download also includes this Technote).




Technote 113: Measuring Sound Pressure Level with APx 1.0.0 (1.20 MB)

Acoustic sounds or noise in the environment is typically measured with a handheld sound level meter. This Technote explains some of the theory behind such measurements, and how to make them instead using an APx analyzer. Using the analyzer adds the capability to perform spectrum analysis, and to visualize the character of the sound signal over time. The latter is especially valuable when measuring non-steady state sounds, such as a pulsating alarm. Requires the APx Sound Level Meter Utility, available as a separate download, to make the measurements.




Technote 111: Testing USB Headsets (38.01 MB)

This Technote discusses techniques for testing the audio performance of USB headsets using an Audio Precision APx analyzer. Includes APx projects and wave files.




Technote 110: Legacy Instrument Migration to APx (1.81 MB)

Addresses conversion of tests and procedures/macros written using AP'€™s Windows-based APWin, AP2700, or ATS software to APx500. If you are using AP'€™s DOS-based S1.EXE software for System One, please refer to Technote 109 instead.




Technote 108: PC Audio Testing (20.51 MB)

This Technote discusses the techniques necessary to perform the "Basic Six" audio measurements on consumer-level PC audio devices. This category includes sound systems integrated into notebooks, netbooks, tablets, and PC motherboards, as well as expansion cards and some external devices. It doesn'€™t include USB-connected headsets, nor pro-audio devices with balanced input and output connections.

Includes APx project and .wav test signal files for playback.




Technote 107: Measuring the Sound Pressure Level of Portable Audio Player Headphones (1.27 MB)

Describes how to measure the sound pressure level developed by portable audio players and their associated headphones, according to British Standard / European Norm 50332. Also shown is how to use the APx Portable Audio Player / Portable Headphone Test Utility to facilitate making the necessary measurements with an APx500 analyzer.

Performing the described tests requires that you download the APx Portable Audio Player / Headphone Test Utility. This Technote is also included in that download.




Technote 106: Measuring PSRR (Power Supply Rejection Ratio) (1.16 MB)

In this technote we describe and compare two different methods to measure PSRR. Then we give instructions for using the APx PSRR Measurement Utility, which simplifies the calculations and graphing on APx analyzers.

This technote is included in the APx PSRR Measurement Utility download.




Technote 105: FM Radio Receiver Testing with APx Audio Analyzers (1.54 MB)

In this technote, we discuss how to test the analog sound quality of FM radio receivers using an Audio Precision APx500 Series audio analyzer. We also discuss how to test the Radio Data System (RDS), which allows text, such as song title and artist, to be transmitted digitally as part of the analog radio signal.