Technical Papers
A collection of published papers by Listen employees and colleagues.
Enhanced Perceptual Rub & Buzz Measurement for Testing Automotive Loudspeakers
/in Papers /by ZarinaLoudspeaker Rub & Buzz faults are a problem for automotive manufacturers as they sound harsh and immediately give the perception of poor quality. There are two places such faults can occur – during speaker manufacturing and installation of the speaker in the car. A buzzing loudspeaker in a car is disappointing to a customer and […]
The Challenges of Testing Voice-Controlled Audio Systems
/in Papers /by ZarinaSmart devices that are voice-controlled such as smart speakers, hearables, and vehicle infotainment systems are notoriously complex to test. They have numerous connections from wired to wireless and contain much signal processing, both on the record and the playback side. This means that their characteristics change according to ‘real world’ conditions of the environment that […]
Testing Audio Performance of Hearables
/in Papers /by ZarinaSmart headphones or “hearables” are designed not only to playback music but to enhance communications in the presence of background noise and in some cases, even compensate for hearing loss. They may also provide voice recognition, medical monitoring, fitness tracking, real-time translation and even augmented reality (AR). They contain complex signal processing and their characteristics […]
A New THD+N Algorithm for Measuring Today’s High Resolution Audio Systems
/in Papers /by ZarinaIn this paper, a mathematical definition of Total Harmonic Distortion + Noise suitable for testing high-resolution digital audio systems is presented. This formal definition of the “distortion analyzer” mentioned in AES17 defines THD+N as the RMS error of fitting a sinusoid to a noisy and distorted sequence of measurements. We present the key theoretical result […]
Evaluation of audio test methods and measurements for end-of-line loudspeaker quality control
/in Papers /by ZarinaIn order to minimize costly warranty repairs, loudspeaker OEMS impose tight specifications and a “total quality” requirement on their part suppliers. At the same time, they also require low prices. This makes it important for driver manufacturers and contract manufacturers to work with their OEM customers to define reasonable specifications and tolerances. They must understand […]
Challenges of IoT Smart Speaker Testing
/in Papers /by ZarinaQuantitatively measuring the audio characteristics of IoT (Internet of Things) smart speakers presents several novel challenges. We discuss overcoming the practical challenges of testing such devices and demonstrate how to measure frequency response, distortion, and other common audio characteristics. In order to make these measurements, several measurement techniques and algorithms are presented that allow us […]
Evaluation of Audio Test Methods and Measurements for End-of-Line Automotive Loudspeaker Quality Control
/in Papers /by ZarinaIn order to minimize costly warranty repairs, automotive manufacturers impose tight specifications and a “total quality” requirement on their part suppliers. At the same time, they also require low prices. This makes it important for automotive manufacturers to work with automotive loudspeaker suppliers to define reasonable specifications and tolerances, and to understand both how the […]
In-Vehicle Audio System Distortion Audibility versus Level and Its Impact on Perceived Sound Quality
/in Papers /by ZarinaAs in-vehicle audio system output level increases, so too does audio distortion. At what level is distortion audible and how is sound quality perceived as level increases? Binaural recordings of musical excerpts played through the in-vehicle audio system at various volume levels were made in the driver’s position. These were adjusted to equal loudness and […]
The Correlation Between Distortion Audibility and Listener Preference in Headphones
/in Papers /by ZarinaIt is well-known that the frequency response of loudspeakers and headphones has a dramatic impact on sound quality and listener preference, but what role does distortion have on perceived sound quality? To answer this question, five popular headphones with varying degrees of distortion were selected and equalized to the same frequency response. Trained listeners compared […]
Advances in Impedance Measurement of Loudspeakers and Headphones
/in Papers /by ZarinaImpedance measurement is often the sole electrical measurement in a battery of QC tests on loudspeakers and headphones. Two test methods are commonly used, single channel and dual channel. Dual Channel measurement offers greater accuracy as both the voltage across the speaker (or headphone) and the reference resistor are measured to calculate the impedance. Single […]
Measurement of Harmonic Distortion Audibility Using A Simplified Psychoacoustic Model – Updated
/in Papers /by ZarinaA perceptual method is proposed for measuring harmonic distortion audibility. This method is similar to the CLEAR (Cepstral Loudness Enhanced Algorithm for Rub & buzz) algorithm previously proposed by the authors as a means of detecting audible Rub & Buzz which is an extreme type of distortion[1,2]. Both methods are based on the Perceptual Evaluation […]
Measurement of Harmonic Distortion Audibility Using A Simplified Psychoacoustic Model
/in Papers /by ZarinaA perceptual method is proposed for measuring harmonic distortion audibility. This method is similar to the CLEAR (Cepstral Loudness Enhanced Algorithm for Rub & buzz) algorithm previously proposed by the authors as a means of detecting audible Rub & Buzz which is an extreme type of distortion[1,2]. Both methods are based on the Perceptual Evaluation […]
Practical Implementation of Perceptual Rub & Buzz Distortion and Experimental Results
/in Papers /by ZarinaIn a previous paper [1], we demonstrated how an auditory perceptual model based on an ITU standard can be used to detect audible Rub & Buzz in loudspeakers using a single tone stimulus. In this paper, we discuss a practical implementation using a stepped sine sweep stimulus and present detailed experimental results on loudspeakers including […]
Practical Measurement of Loudspeaker Distortion Using a Simplified Auditory Perceptual Model
/in Papers /by ZarinaManufacturing defects in loudspeaker production can often be identified by an increase in Rub & Buzz distortion. This type of distortion is quite noticeable because it contributes an edgy sound to the reproduction and is annoying because it often sounds separate or disembodied from the fundamental signal. The annoyance of Rub & Buzz distortion is […]
Evolution of Time-Frequency Analysis Methods and their Practical Applications
/in Papers /by ZarinaTime-Frequency analysis has been in use for more than 20 years and many different Time-Frequency distributions have been developed. Four in particular, Short Time Fourier Transform, Cumulative Spectral Decay, Wavelet and Wigner-Ville have gained popularity and firmly established themselves as useful measurement tools. This paper compares these four popular transforms, explains their trade-offs and discusses […]
Challenges of MP3 Player Testing
/in Papers /by ZarinaMP3 player audio performance is discussed including measurements of frequency response, phase response, crosstalk, distortion, sampling rate errors, jitter, and maximum sound pressure level with headphones. In order to make these measurements, several measurement techniques and algorithms are presented to overcome some of the challenges of testing MP3 players. We discuss test equipment requirements, selection […]
A New Method for Measuring Distortion using a Multitone Stimulus and Non-Coherence
/in Papers /by ZarinaA new approach for measuring distortion based on dual-channel analysis of non-coherence between a stimulus and response is presented. This method is easy to implement, provides a continuous distortion curve against frequency, and can be used with a multitone stimulus, noise, or even music. Multitone is a desirable test signal for fast frequency response measurements […]
Higher Order Harmonic Signature Analysis for Loudspeaker Defect Detection
/in Papers /by ZarinaLoudspeaker assembly faults, such as a rubbing voice coil, bent frame, loose spider, etc., have traditionally been detected using experienced human listeners at the end of a production line. Previous attempts to develop production measurement systems for on-line testing typically analyze only low-order harmonics for the primary purpose of measuring total harmonic distortion (THD), and […]
Enhancements for Loose Particle Detection
/in Papers /by ZarinaDuring loudspeaker production, particles may become trapped in the loudspeaker motor and voice coil vicinity, resulting in a distinctive defect that is easily heard, but difficult to detect by traditional test and measurements. We found that a Sine Sweep Stimulus followed by a High Pass Filter and RMS Envelope Analysis efficiently detected Loose Particles and […]
Loose Particle Detection
/in Papers, Uncategorized /by ZarinaDuring the loudspeaker manufacturing process, particles may become trapped inside the loudspeaker, resulting in a distinctive defect that is easily heard but difficult to measure. To give a clearer view of the problem, Time-Frequency maps are shown for some defective loudspeakers. Based on this analysis, a reliable testing procedure using a swept-sine stimulus, high-pass filter, […]
Simultaneous measurement of impulse response and distortion with a swept-sine technique
/in Papers /by ZarinaThis landmark paper by Angelo Farina discusses the benefits of the Log Sine Sweep (also known as Frequency Log Sweep or Log Chirp), one of the test signals available in SoundCheck. A novel measurement technique of the transfer function of weakly not-linear, approximately time-invariant systems is presented. The method is implemented with low-cost instrumentation; it […]
Virtual Instruments for Audio Testing
/in Papers /by ZarinaAlthough Virtual Instruments have been part of SoundCheck as long as most of us can remember, back in 1998 this was a huge innovation. This paper introduces the concept at a time when computerized audio measurement was a novel concept. Authors: Steve Temme Presented at the 105th AES Convention, San Francisco, 1998 Full Paper
How to Graph Distortion Measurements
/in Papers /by ZarinaDistortion curves are conventionally plotted under the corresponding excitation frequency of the measured fundamental. Interpretation of results can be misleading due to the influence that the passband shape and amplitude irregularities of the fundamental response have on the distortion responses. By ‘amplitude normalizing’ the distortion responses to the measured fundamental response before plotting them at […]
Simulated Free Field Measurements
/in Papers /by ZarinaThe development of time selective techniques has enabled measurements of the free field response of a loudspeaker to be performed without the need for an anechoic chamber. The low frequency resolution of both time selective techniques and anechoic measurements is, however, limited by the size of the room. A technique is presented enabling measurements of […]
