Listen, Inc. Celebrates 25 Years of Innovation

AmpConnect 621 is a rugged 6-in, 2 out high resolution audio interface specifically developed for multichannel audio test applications such as automotive audio, sound power measurements, and measuring devices with multiple speakers such as smart phones or sound bars. In addition to 6 inputs and 2 outputs, AmpConnect 621 offers amplifier output, microphone power, full TEDS calibration support, impedance measurement and digital I/O in a single USB-connected unit.

Designed for seamless integration with SoundCheck, it is controlled via the SoundCheck software only. Setup is fully automatic, and there are no front panel buttons, eliminating the possibility of accidental changes to the settings and making it ideal for production applications.

TEDS Calibration Support (with compatible Listen hardware) enables automatic identification, configuration and calibration of TEDS microphones and accelerometers, saving time on initial hardware setup and whenever hardware is changed.

Listen offers a test sequence to calibrate a 4.1 speaker array to conform with the ETSI ES 202 396-1 standard. This is considerably less expensive than stand-alone background noise systems, and has the added advantage that it can be integrated into test sequences.

Stepped sine amplitude and frequency sweeps can be equalized for a smooth transition between steps. This minimizes the transient response in the device under test, resulting in faster measurements.

A new real time distortion analyzer enables distortion, including THD and THD+N, THD and THD+N residual level, and SINAD, to be quickly viewed in real time without having to configure a sequence. A, B, and C weighting filters along with user-defined arbitrary weighting functions can be applied. Data from the distortion analyzer can also be saved and, with the strip chart recorder module installed, viewed over time.

SoundCheck now offers powerful external control with TCP/IP (in addition to Active X). This enables SoundCheck to be controlled  via any programming language, on any operating system, either locally or through a network. This powerful and expandable command format offers huge benefits for factory automation as a single computer can control multiple SoundCheck systems.

This was further expanded in 2020 with the new sequence parameter feature, which allows the user to use TCP/IP  commands to pass test configuration data into the memory list from external programs. By externally storing parameters such as limits, test levels, and test signals, a single sequence can be used for multiple products, simplifying the number of sequences that a large organization needs to maintain, and reducing test configuration time. It is also useful for applications where a sequence needs to be run many times with different parameters, for example, testing voice recognition with a range of voices or test levels.

SoundCheck is the first commercially available large-scale audio test solution to run under the Mac operating system. Sequences, steps, and data files are cross compatible between the Windows and Mac versions, providing versatility when collaborating with other SoundCheck users, and Core audio driver support allows the same hardware to be used on both operating systems.

Listen’s new entry level SoundCheck package consists of an audio interface packaged with a simplified version of the SoundCheck software. SoundCheck ONE includes sequence templates that are used to generate product-specific sequences by selecting parameters such as the stimulus signal, characteristics to be measured, frequency range, level and limits. This makes the system very simple to use, in addition to being extremely cost-effective. It can be upgraded to a higher level SoundCheck package at any time.

AudioConnect 4×4 is a high accuracy 4-in, 4-out audio interface specifically for audio test and measurement. Controls are simple – a single USB connection and a power indicator – all other typical soundcard controls have been eliminated to make operation and calibration simple and error-free.

Listen partners with Portland Tool and Die to offer innovative interfaces that enable products such as Bluetooth and MEMS microphones to be tested. These can be fully controlled via SoundCheck, expanding the system’s test capabilities.

Time Domain Waveform Filters allow a curve from the memory list to be convolved with a waveform in the memory list to create a new waveform that has its spectral content shaped by the selected curve. There is also an option for minimum phase and inverting the curve. This may be used, for example, for measuring the A-weighted peak acoustic pressure of a waveform. The A-weighting curve is first applied to the acoustic waveform via the waveform filtering post processing step, and then the peak value of the resulting waveform is measured. This method is used in the IEEE 269 and TIA 920 telephony standards.

Listen is the first company to offer perceptual Rub & Buzz measurements to detect only those Rub & Buzz faults that would be heard by the human ear. The CLEAR  (Cepstral Loudness Enhanced Algorithm for Rub & Buzz) algorithm offers true perceptual Rub & Buzz analysis using a simplified auditory perceptual model to measure the loudness of Rub & Buzz distortion in phons rather than the more traditional dB SPL and % distortion units. This better identifies whether distortion due to manufacturing defects can be heard by the listener than conventional measurements. In addition to a result which corresponds more accurately to the human ear, this new test method is also less sensitive to transient background noises than traditional methods, and it is much simpler to set limits.

The signal generator now offers wavefile streaming with real time equalization. This removes memory limitations on the length of test signals, which means that longer test signals such as those required for analysis of speech and music can easily be accommodated.

Listen was the first to introduce Open Loop testing – testing a device where the stimulus and response are asynchronous. This method was originally developed to test MP3 players, and involved loading a test signal onto the device, then using a triggered acquisition step to capture the response. These days, open loop testing is most widely used for testing voice-activated devices such as smart speakers, automotive audio, hearables and more. SoundCheck’s algorithms have evolved over the years and now include sophisticated frequency and chirp triggers, advanced auto-delay algorithms and more.

Listen is the first to offer the ability to play a conditioning signal right before the excitation signal. This enables a speaker to be tested in steady state conditions, for example by playing pink noise first to warm up the speaker, or in telephony applications it enables a signal to be used to trigger a voice activity detector before beginning recording. The conditioning signal is excluded from the response analysis. In more recent years, this same stimulus flexibility has allowed the use of sophisticated stimuli for open loop test sequences for smart and voice-activated devices.

Listen was the first test and measurement system to offer an algorithm for the measurement of non-coherent distortion using music as the test signal. This algorithm uses the transfer function to examine the part of the response that is not coherent with the stimulus, enabling total distortion versus frequency to be measured under real world conditions using signals such as music or speech.

DC Connect is USB controlled precision DC power supply and current monitor. It enables high resolution dynamic measurements of voltage and current consumption in portable electronic devices such as hearables,  hearing aids, microphones, cell phones, and other battery powered electronic devices. Equally suitable for R&D and production line use, full software control, enables the output level to be changed rapidly during a test to enable measurement of current consumption while varying frequency and amplitude of the test signal.

The Log TSR measurement method (also known as ‘Farina Sweep’ or ‘Log Chirp’) was already under development in SoundCheck when Angelo Farina presented his landmark paper on the subject, so within weeks of this method reaching a wider audience, SoundCheck had the first commercial implementation Log TSR measurement methods – a technique still extensively used today for making fast measurements. This continuous log sine sweep from low to high covers every frequency in the chosen range using the same time (and energy) for every octave, which achieves a good signal to noise ratio across all frequencies. Since the sweep rate is slow at low frequencies but increases with frequency, distortion is accurately measured at low frequencies while retaining a fast test speed and high throughput. This makes it a common choice for rapid loudspeaker production line measurements of fundamental response and distortion. Used together with a Time Selective Response algorithm, simulated free field measurements can be made. This technique enables anechoic chamber measurements to be made in a normal room with no loss of accuracy.

Listen is the first test and measurement system to feature virtual instruments – software equivalents of a signal generator, multimeter, real time analyzer, oscilloscope and spectrum analyzer. These virtual instruments can be programmed and used within test sequences, or used as stand-alone instruments. Multiple instances of the same instrument can even be opened simultaneously, enabling real time live data to be viewed in multi-channel applications.  This naturally makes for an extremely compact and flexible setup for the laboratory, traveling, and these days, working from home. In more recent years, the instrument panel was expanded with the addition of a real time distortion analyzer and virtual chart recorder.

Listen is first to incorporate an Autodelay algorithm. This automatically compensates for the delay between stimulus and response, displaying the result in time, samples and distance. It also measures signal polarity. Although the initial application of this algorithm was to measure the distance from and align the loudspeaker to the measurement microphone, these days it is invaluable for testing open-loop devices with huge latencies.

SoundCheck is the first test system to detect Rub & Buzz by measuring over 200 high order harmonics both individually and simultaneously (rather than simple high pass filters which lump harmonics and noise together). This revolutionary method enables a high degree of selectivity in the analysis options, enabling specific faults to be identified and detected. For example, rub & buzz due to lead wires hitting a speaker cone usually occurs at the 50th harmonic and above, whereas a rubbing voice coil occurs mostly in 10-15th harmonic.

The HarmonicTrak algorithm is the first audio measurement algorithm to dramatically decrease measurement time by measuring the fundamental and the harmonics of a stepped sine stimulus in parallel (over 10x faster than a Brüel and Kjær 2012). We believe we are still the only people using this algorithm today.

Listen began the software-based audio test revolution when it became the first company to launch a commercial software-based audio test system that would work with any hardware and audio interface, eliminating the need for expensive proprietary hardware. The first version of SoundCheck used an off-the-shelf NI data acquisition card, and by mid 1996, Listen was the first company to offer a professional soundcard-based measurement system. Listen’s software has always worked with any soundcard/audio interface and any test hardware, keeping flexibility high and the cost of ownership low. Today, Listen offers its own audio interfaces with additional features to simplify audio test, as well as remaining compatible with, and supporting soundcards and data acquisition cards with ASIO, Core Audio, WASAPI, WDM, DAQmx and other communications protocols from multiple manufacturers.