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Each Audio Precision Technote is a focused look at a single topic in audio test and measurement—sometimes a particular solution, perhaps a time-saving tip or an in-depth exploration of a difficult concept. Many of the Technotes are specific to Audio Precision analyzers, and some to a particular instrument. However, the approaches and strategies taken in a certain testing environment are often transferrable to another situation, and our customers find value even the older Technotes written for legacy instruments.

Each Technote is in the form of an Adobe Acrobat PDF; some Technotes include test files for a particular Audio Precision audio analyzer system as a second download, linked by "All files."

#	File	Description
103	Download File TN-103.pdf (490 kB) All Files (780 kB)	Dolby Digital Testing using the Audio Precision 2700 Series This Technote describes a set of over 30 AP Basic macros created to make it easier to take measurements required for Dolby Digital Certification.
102	Download File TN-102.pdf (483 kB) All files (8.6 MB)	Testing Personal Media players using QuickTest This Technote describes the ATS and AP2700 Series QuickTest application. QuickTest allows users to run comprehensive tests for personal media players quickly and easily. QuickTest measures DC offset, output level, distortion, frequency response, phase deviation, noise and crosstalk, and compares the results to defined pass / fail limits. These results, with identifying information, are displayed on-screen and saved in a file for post-test review.
101	Download File TN-101.pdf (1.3 MB) All files (1.2 MB)	LabVIEW ActiveX Automation for Audio Precision instruments Basic principles and techniques needed to control an Audio Precision instrument using the control software (AP2700, ATS or APWIN) as an ActiveX automation server from within the NI LabView environment. Technote 101 is a revision of Technote 22.
30	Download File TN-30.pdf (310 kB) All files (398 kB)	.WAV file Import This APWIN utility allows you to load any .wav files compatible with the Microsoft RIFF file format into APWIN and analyze them in the frequency or time domain.
29	Download File TN-29.pdf (310 kB) All files (398 kB)	Computing Group Delay This macro, entitled Group delay.apb, will compute and display the relative input-output time delay of a device as a function of frequency.
28	Download File TN-28.pdf (161 kB) All files (176 kB)	Measurement Microphone dB SPL Calibration Utility to set measurement microphone reference level so dBr = dBspl.
27	Download File TN-27.pdf (66 kB) All files (100 kB)	Polarity test Utility to test polarity between analog generator outputs and analog analyzer inputs.
26 25 24 23	------------ ------------ ------------ ------------	These four Technotes by the late Julian Dunn have been updated and published together as Measurement Techniques for Digital Audio.
22	------------	This Technote has been revised and republished as Technote 101.
21	Download File TN-21.pdf (213 kB)	Obtaining Frequency Response Measurements Using an Audio Program as the Test Signal This Technote describes the measurement of frequency response with System Two’s dual-channel FFT using power spectrum averaging, which allows wide-band program material, such as music, to be used as the test signal.
20	Download File TN-20.pdf (195 kB)	Return Loss Measurements This Technote gives an overview of the concept of return loss in telephony. Return loss is an expression of the impedance mismatch in a transmission circuit which can give rise to reflection of signal energy. Sample hybrid circuits and their use in return loss measurements using Audio Precision instruments are described.
19	Download File TN-19.pdf (263 kB)	Create an HTML-Based Help System for AP Basic Macros This TECHNOTE is a short primer in using AP Basic to create and use the webBrowser ActiveX object to create a sophisticated HTML-based help system to guide production technicians through AP Basic macros.
18	Download File TN-18.pdf (145 kB) All files (160 kB)	Multitone Waveform Creation Utility for Use with FASTTEST This Technotebes the Makewave utility, an AP Basic procedure that simplifies the process of creating multitone waveform files to use with the analog and digital generators in System One and System Two instruments.
17	Download File TN-17.pdf (309 kB) All files (150 kB)	Computing THD Measurements from FFT Data Using THD.exe Conventional analog total harmonic distortion tests are made with a notch filter that removes the fundamental and makes a root sum square summation of all of the harmonics. FFT techniques, on the other hand, provide the absolute amplitude of each individual harmonic. This program will extract the necessary harmonic data and the fundamental amplitude, compute the rss summation and express the result as a conventional THD ratiometric value.
16	--------------------	Under revision.
15	Download File TN-15.pdf (3.5 MB) All files (744 kB)	GPIB Communication from AP Basic This Technote describes how to setup communication between AP Basic and GPIB instrumentation (using the National Instruments GPIB Interface).
14	Download File TN-14.pdf (2.1 MB) All files (1.2 MB)	Testing Reduced Bit-Rate Codecs Using the System One DSP Program CODEC.dsp Reduced bit rate codecs cannot be properly tested using conventional sine wave test signals. Using multitone test signals and FFT analysis, the codec can be stressed to properly characterize how it will perform with program material. CODEC.dsp uses multitone testing techniques and internal automatic masking curve generation to facilitate objective and repeatable evaluation of codecs.
13	Download File TN-13.pdf (1.3 MB) All files (788 kB)	PC Sound Card Testing Using DSP-RIFF.exe Waveform Conversion Utility The multimedia expansion in the PC industry has created the need to test the audio performance of sound cards. This is a classic dual-domain application requiring testing of the D-to-A and A-to-D sections. This utility will translate either direction between the Microsoft RIFF .WAV file format and the Audio Precision DSP.WAV file format. This allows a System One test signal created by MAKEWAVE to be played back though the D-to-A, and a captured PC .WAV file to be analyzed on System One.
12	Download File TN-12.pdf (167 kB) All files (100 kB)	Creating Arbitrary Waveforms Using Time Record data System One DSP can produce signals based on a stored waveform loaded into its memory. A file with a .wav extension is downloaded to the DSP memory in System One to create the output. A utility called MAKEWAVE.exe is supplied With System One DSP that will convert an ASCII file that contains a time record into the .WAV format for use with the DSP generator. This Technote describes the format of the .waa ASCII files and how to create arbitrary waveforms. It assumes some programming knowledge.
11	Download File TN-11.pdf (740 kB)	Remote Test Data Retrieval: Send a FAX This Technote describes how to set up the PC that controls System One to be able to automatically send a fax to a designated fax machine with the results, in both tabular and graphical form, of the measured data. The measuring PC can be at a remote unattended location as the fax capability can be configured to operate completely automatically on time, event of data out-of-limits conditions. The description shows how to integrate commercial fax modem cards and software.
10	Download File TN-10.pdf (167 kB) All files (140 kB)	SWR-122 Series Switchers APIB Interface Description System One SWR series switchers are normally controlled via the APIB interface and S1.exe software. This Technote describes the APIB interface used on the switchers and explains how to control them from a generalized parallel port. A sample BASIC program is included to program the switchers from a PC parallel printer port. This Technote assumes programming and hardware knowledge.
9	Download File TN-9.pdf (171 kB) All files (135 kB)	Restructuring Multitrack Data Using MTRACKFR.exe Frequency response measurements on a Multitrack tape recorder are best made by successively measuring each track at the first frequency, then step to the second frequency and measure all tracks, and so on until all frequencies are measured. This produces a nested sweep file that plots amplitude versus track rather that amplitude versus frequency. This Technote contains a program that will restructure such data into the preferred format
8	Download File TN-8.pdf (131 kB)	Programmers’ Reference to S1.exe DSP Waveform File Format System One DSP programs allow a SAVE WAVEFORM operation to store the time record data to disk. This Technote describes the internal structure of the *.wav files so produced. This would allow a knowledgeable programmer to extract data from this file for external post processing. It assumes intermediate programming expertise.
7	Download File TN-7.pdf (139 kB)	Programmers’ Reference to S1.exe internal *.tst file format S1.exe *.tst files save instrument setups and test data in a binary format for space and speed efficiency. It is possible to examine such a file (or *.lim, *.eq, *.swp and *.ovl files) to extract this data. This Technote explains the internal structure of these files. It assumes intermediate programmers knowledge and is intended as a reference source, not a step-by-step explanation.
6	Download File TN-6.pdf (146 kB) All files (120 kB)	Computing Statistical Data From Nested Sweeps Using NSWEEP.exe When several plots of a parameter are acquired, it is often useful to reduce the large volume of data to statistical summaries such as maximum, minimum, average or delta. This Technote includes a program that will operate on an S1.exe nested sweep file to produce the statistical data mentioned above. The program can be run in an S1.exe DOS shell.
5	Download File TN-5.pdf (159 kB) All files (110 kB)	Usage Instructions for COMBINEC.EXE System One produces data files that are two or three columns wide with as many rows as measurement steps. Usually the first column is the source data and columns two and three are measured data. There are some applications where it is desirable to use some data from one file with data from another file to produce a third file. This Technote includes a C program that allows columnar data to be exchanged, moved or combined to produce a new data file.
4	Download File TN-4.pdf (133 kB) All files (111 kB)	Computing Equalization Curves Using EQCURVE.EXE Tests of recorded or transmission media often require an equalized generator signal. Modifying the response of a swept generator to reciprocate the pre-emphasis or de-emphasis characteristics of the device under test will prevent overload and yield a flat response at the output. This Technote includes a BASIC program that will compute a data file based on user supplied time constants. The data file can then be used as an S1.exe EQ curve.
3	Download File TN-3.pdf (232 kB)	Remote Site Data Retrieval of Test Results Using Modems Some measurement situations place the measurement equipment at some distance from the operator. Many broadcast applications require that System One be located at a distant, possibly unattended site. This Technote describes how to set up a modem communication link between the distant measurement PC and a local operator PC to enable manual or automatic transfer of measured data. The set up for two commercial communication programs, PC Tools Commute and Norton pcAnywhere, are described.
2	Download File TN-2.pdf (184 kB) All files (148 kB)	Generating Group Delay vs. Frequency Plots Plots of group delay versus frequency are useful in filter design and loudspeaker design applications. This Technote includes a BASIC program that will use a phase versus frequency plot as generated by System One to produce a group delay plot. The BASIC program can be run in a DOS shell within S1.exe.
1a	Download File TN-1a.pdf (191 kB) All files (114 kB)	Generating Impedance vs. Frequency Plots with APWIN This Technote is a rewrite of Technote #1 to support System One and System Two using Windows APWIN software. An additional method using an external amplifier and current sense resistor is provided.
1	Download File TN-1.pdf (176 kB) All files (139 kB)	Generating Impedance vs. Frequency Plots with System One Describes how to generate Impedance versus Frequency swept data using System One. This is of particular interest to loudspeaker designers where the impedance response can provide very useful information on the performance of a speaker. Includes a BASIC program that does the calculations.

Run comprehensive tests for personal media players quickly and easily, measuring DC offset, output level, distortion, frequency response, phase deviation, noise and crosstalk. More...