About the project
Development of psychoacoustic models: Sharpness and Impulsiveness
Background: Sound quality metrics (SQMs) are often used to analyse complex sound scenarios, e.g., for soundscape applications. SQMs have also been widely applied to improve the sound quality of different consumer products, especially in the automotive industry. SQMs, such as loudness, sharpness, tonality, roughness, and fluctuation strength are good indicators of how the human auditory system reacts to different features of acoustic stimuli.
Sound quality can also affect the health and well-being of people in a given environment. Therefore, it is of the utmost importance that the definition of good sound quality in a given context is as precise as possible. In this regard, psychoacoustic indicators are usually used to develop these metrics.
In recent years, several psychoacoustic standards have been published based on the Sottek Hearing Model: the SHM Loudness, a new approach to time-varying loudness based on a nonlinear combination of partial tonal and noise loudness (as part of the SHM Tonality, standardised in ECMA 418-2) to better account for the fact that the loudness of the tonal components, i.e., tonal loudness, may have a stronger influence on loudness perception than the loudness caused by the other components, i.e., noise loudness. In addition, there are standards for psychoacoustic modulation analysis: the SHM Roughness for the assessment of fast modulated sounds (standardised in ECMA 418-2) and the SHM Fluctuation Strength, an adapted model for slow modulated sounds (to be standardised in 2025).
Research Gaps: Other very important psychoacoustic parameters are sharpness and impulsiveness. Existing sharpness models have some drawbacks: for example, they do not adequately account for loudness and temporal effects, and they do not provide sharpness values that linearly correspond to human perception. In addition, there is only a German standard for stationary sounds and no standard for time-varying sounds. For impulsiveness there is currently no standard, but a model based on the Sottek Hearing Model published in 1993.
Existing models assume simple sound field situations such as free field or diffuse field. These situations are extremely rare, but an equalisation procedure can be applied to binaurally recorded signals so that the binaural signals then approximately correspond to a simple microphone recording. Normal measurement conditions in rooms or small enclosures like vehicle interiors yield results that are far from single-microphone recordings with different signals for each ear. In this case, the equalisation is often performed under the assumption of one of the above sound fields, which leads to approximate solutions. A better solution is to use signals measured directly in the ear canal. This requires updated models with new robust reference points: jury tests with human subjects together with measurements in the ear canal and numerical simulations.
Research Aim and Objectives:
This PhD is aimed at developing Improved models of sharpness and impulsiveness based on the recently standardised Sottek Hearing Model. Specific objectives are:
- Development of improved models for sharpness and impulsiveness, taking into account dependencies on loudness and temporal effects, with the aim of providing models for psychoacoustic parameters whose results correspond linearly to human perception.
- Optimisation of the modelling for arbitrary sound fields by targeted search for suitable reference points for the microphones.
- Validation by listening tests.
Requirements for the PhD Candidate: The research would suit graduates in acoustics, audiology (and any other relevant disciplines) with a solid understanding and expertise in signal processing and coding. Experience in mathematical modelling and psycho-physics will be useful. This project will allow a motivated PhD student to develop highly impactful psychoacoustic models, which will be used widely both in academia and industry worldwide.
Supervisors
- Professor Antonio Torija Martinez and Dr Zuzanna Podwinska, University of Salford
- Project Partner: HEAD Acoustics
