Preface

"*There is no such thing as an easy experiment, nor is there any substitute for careful experimentation in many areas of basic research and applied product development.*" From Experimental Methods for Engineers by J. P. Holman

Measurement is a multidisciplinary experimental science. Measurement systems synergistically blend science, engineering and statistical methods to provide fundamental data for research, design and development, control of processes and operations, and facilitate safe and economic performance of systems. In recent years, measuring techniques have expanded rapidly and gained maturity, through extensive research activities and hardware advancements.

With individual chapters authored by eminent professionals in their respective topics, **Advanced Topics in Measurements** attempts to provide a comprehensive presentation on some of the key applied and advanced topics in measurements for scientists, engineers and educators. These two books illustrate the diversity of measurement systems, and provide in-depth guidance for specific practical problems and applications.

I wish to express my gratitude to the authors of the chapters for their valuable and highly professional contributions. I am very grateful to Ms. Gorana Scerbe and Ms. Mirna Cvijic, publishing process managers of the present project and the editorial and production staff at InTech.

Finally, I wish to acknowledge and appreciate the patience and understanding of my family.

> **Prof. Md. Zahurul Haq, Ph.D.** Department of Mechanical Engineering Bangladesh University of Engineering and Technology Dhaka Bangladesh

**1** 

*Poland* 

**System for High Speed Measurement** 

Andrzej B. Dobrucki, Przemysław Plaskota and Piotr Pruchnicki

Recently surround-sound systems have become popular. The effect of "surrounding" the listener in sound is achieved by employing acoustic phenomena which influence localizing the source of the sound. Similarly to stereophony system the time, volume and phase interrelations in signals coming from each sound source are taken into account. Additionally the influence of the acoustic system created by the pinna, head and torso on the frequency characteristic of the sound is taken into consideration. This influence is described by the Head-Related Transfer Function (HRTF). The knowledge of the human physical body characteristics' influence on the perception of the sound source location in space is being

So far the best method of including the influence of the human body on the frequency characteristic of the sound is the HRTF measurement for different locations of the sound in relation to the listener. Then the achieved measurement results are used for creating a database meant for the sound reproduction. Creating a proper HRTF database is a difficult problem – every human exhibits individual body characteristics therefore it is not possible to create one universal database for all the listeners. For this reason applying the knowledge of the human body influence on the frequency characteristic of the sound is impeded. In order to include these parameters it is necessary to conduct all these laborious

The HRTF is a representation of the influence of the acoustic system formed by the pinna, head and human torso on the deformation of the acoustic signal spectrum reaching the listener's ear. The head's shape and tissue structure have a bearing on acoustic signal spectrum distortion (Batteau, 1967; Blauert, 1997; Hartmann, 1999; Moore, 1997). The changes in the spectrum enable the listener is able to more accurately localize the sound source in the space which surrounds her/him. In case of headphone listening the influence of the acoustic system formed by the pinna, head and human torso is eliminated and the acoustic signal received by the listener is unnatural – the listener localizes the sound source inside her/his head. Through the use of HRTF measurement results the signal can be so deformed that the listener subjectively identifies the spatial properties of the sound whereby the location of the sound source in the space surrounding the listener is

more and more frequently applied to building sound systems.

measurements for each individual.

**2. Head-Related Transfer Function** 

**1. Introduction** 

**of Head-Related Transfer Function** 

*Wroclaw University of Technology* 
