Neurally Based Measurement and Evaluation of Environmental Noise

Neurally Based Measurement and Evaluation of Environmental Noise
Yoshiharu Soeta and Yoichi Ando
Springer, Japan, (2015)
264 pp., hardbound, 129 USD
ISBN: 978-4-431-55431-5
eBook, 99.00 USD

This book is the compilation of the research results gained during 40 years of work by the authors, namely by Yoichi Ando from Kobe University (Japan), on the measurement and evaluation of environmental noise based on an auditory neural and brain-oriented model. Ando is known to the acoustics community by the books Concert Hall Acoustics (1985) and Architectural Acoustics (1998), and from numerous scientific papers as one of the main contributors establishing the so-called “subjective preference theory” describing hearing sensations. The basic idea of this theory is that the auto-correlation function (ACF) and the interaural cross-correlation function (IACF) for audible signals arriving at both ears provide a representation for judging the subjective preference and the spatial sensations of sounds and noises.

The book, besides an introduction, is structured into nine chapters. Each chapter ends with a very extensive reference list, which is referred to in the chapter’s text. The chapters are described here.

“Signal Processing Model of Human Auditory System” describes the auto-correlation model of the auditory system as developed by Ando, covering also the relation to loudness and to the much more complex term “annoyance.” The majority of the studies by the authors included use factor analysis as a method.

“Noise Measurement Method Based on the Model” introduces auto-correlation function and interaural auto-correlation function, first used by Ando in 2001, to describe sound quality on a subjective basis. These studies lead to an auditory brain model enabling calculation of ACF and IACF on a personal computer from real-time data.

“Temporal Primary Sensations of Noise” and “Spatial Primary Sensations of Noise” both study attributes enabling the ability to distinguish sounds independent of location (i.e., temporal) or dependent on location (i.e., spatial). Time-dependent sensations such as pitch, loudness, timbre, and duration can, based on Ando’s theory, be extracted as temporal factors from the auto-correlation function. This holds as well for factors describing spatial sensation based on IACF. Both chapters describe a neuropsychological model for temporal and spatial sensations, and explain studies performed with test persons to prove the validity of the model. The chapter on spatial sensations also uses the parameter Apparent Source Width (ASW) as a subjective attribute being used to evaluate the room acoustical performance of concert halls and opera houses.

“Noise Measurements” uses conventional parameters for describing noise (e.g., SPL and NC) and, on the other hand, ACF and IACF to characterize different kinds of noises by measurements such as aircraft noise, road traffic noise, flushing toilet noise, railway noise in train stations and in train cars as well, and to footfall noise on floors in buildings.

“Annoyance of Noise” applies the concept of subjective preference to establish some heuristic scale value to different kinds of noises such as pure tones, band-pass noises, and noise in relation to spatial factor (e.g., due to IACC fluctuations). Following the previous chapter, the annoyance resulting from this concept is studied for the noise types already discussed. The chapter closes with a “general equation for annoyance,” enabling the calculation of a scale factor that is the sum of two scale factors, one for the left ear, and one for the right.

“Short-Term Effects of Noise” studies the effect of noise (again described by ACF and IACF) on short-term effects such as speech and sleep disturbance. The experiment correlates the results from listening tests using syllables with measured ACF and IACC data obtained in an anechoic chamber. Finally, cases of nonidentification measured vs. calculated are compared. Further studies refer to the effect of noises even at low levels, or the subjective duration of noises in relation to their SPL (e.g., with sound/noise being present, “time passes faster than in silence”).

“Long-Term Effects of Noise” reviews literature on long-term effects of noise on measurable factors such as human placental latogen, birth weight, reaction of sleeping babies (by PLG and EEG), and effect on height growth of children.

“Application to Sound Design” discusses rules based on ACF and IACC for sound design. For example, the subjective diffuseness of music is discussed. This leads to the path of listening experiments using a binaural auralization of music and sounds, thus not requiring a real room or a setup requiring the knowledge of where to place the listener. Further, the authors study such an arrangement to evaluate the effect of background noises on the listening level of music in train cars. The chapter closes with the subjective preference for birdsongs, which indicates that birdsongs could improve pleasantness of a soundscape. The most pleasant birdsongs are performed by cuckoo and Japanese grosbeak—no wonder.

The book closes with some 14 lines of text on “Urban Soundscape Design,” mentioning that a clear definition of the term “soundscape” is still missing. This, however, is no longer fully correct since ISO/TC43/SC1 has published ISO/DIS 12913–1, “Acoustics—Soundscape—Part 1: Definition and Conceptual Framework” in July 2013. Now, at least, two pages with terms and definitions on soundscapes exist. A second part is in committee draft stage (ISO/CD 12913–2, “Acoustics—Soundscape—Part 2: Data Collection” in July 2016), providing more and detailed guidance on how to perform soundscape studies.

To conclude, this book gives a detailed overview of the achievements in the evaluation of noise based on the subjective preference theory. Certainly, the book does not focus on consulting engineers or acousticians in industry or administration since it focuses very much on details of correlation-based models of the hearing system. It gives, however, a complete overview of the state of the art on this subject, being most relevant to students and scientists working in the field of auditory models.

Heinrich Metzen
Datakustik Greifenberg