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This chapter summarizes and explains key concepts of building acoustics. These issues include the behavior of sound waves in rooms, the most commonly used rating systems for sound and sound control in buildings, the most common noise sources found in buildings, practical noise control methods for these sources, and the specific topic of office acoustics. Common noise issues for multi-dwelling units can be derived from most of the sections of this chapter. Books can be and have been written on each of these topics, so the purpose of this chapter is to summarize this information and provide appropriate resources for further exploration of each topic.

The analysis of sound in the peripheral auditory system solves three important problems. First, sound energy impinging on the head must be captured and presented to the transduction apparatus in the ear as a suitable mechanical signal; second, this mechanical signal needs to be transduced into a neural representation that can be used by the brain; third, the resulting neural representation needs to be analyzed by central neurons to extract information useful to the animal. This chapter provides an overview of some aspects of the first two of these processes. The description is entirely focused on the mammalian auditory system, primarily on human hearing and on the hearing of a few commonly used laboratory animals (mainly rodents and carnivores). Useful summaries of non-mammalian hearing are available []. Because of the large size of the literature, review papers are referenced wherever possible.

Psychoacoustics is concerned with the relationships between the physical characteristics of sounds and their perceptual attributes. This chapter describes: the absolute sensitivity of the auditory system for detecting weak sounds and how that sensitivity varies with frequency; the frequency selectivity of the auditory system (the ability to resolve or the sinusoidal components in a complex sound) and its characterization in terms of an array of auditory filters; the processes that influence the masking of one sound by another; the range of sound levels that can be processed by the auditory system; the perception and modeling of loudness; level discrimination; the temporal resolution of the auditory system (the ability to detect changes over time); the perception and modeling of pitch for pure and complex tones; the perception of timbre for steady and time-varying sounds; the perception of space and sound localization; and the mechanisms underlying that allow the construction of percepts corresponding to individual sounds sources when listening to complex mixtures of sounds.

Signal processing refers to the acquisition, storage, display, and generation of signals – also to the extraction of information from signals and the re-encoding of information. As such, signal processing in some form is an essential element in the practice of all aspects of acoustics. Signal processing algorithms enable acousticians to separate signals from noise, to perform automatic speech recognition, or to compress information for more efficient storage or transmission. Signal processing concepts are the blocks used to build models of speech and hearing. As we enter the 21st century, all signal processing is effectively digital signal processing. Widespread access to high-speed processing, massive memory, and inexpensive software makes signal processing procedures of enormous sophistication and power available to anyone who wants to use them. Because advanced signal processing is now accessible to everybody, there is a need for primers that introduce basic mathematical concepts that underlie the digital algorithms. The present handbook chapter is intended to serve such a purpose.

The chapter emphasizes careful definition of essential terms used in the description of signals per international standards. It introduces the Fourier series for signals that are periodic and the Fourier transform for signals that are not. Both begin with analog, continuous signals, appropriate for the real acoustical world. Emphasis is placed on the consequences of signal symmetry and on formal relationships. The autocorrelation function is related to the energy and power spectra for finite-duration and infinite-duration signals. The chapter provides careful definitions of statistical terms, moments, and single- and multi-variate distributions. The Hilbert transform is introduced, again in terms of continuous functions. It is applied both to the development of the analytic signal - envelope and phase - and to the dispersion relations for linear, time-invariant systems. The bare essentials of filtering are presented, mostly to provide real-world examples of fundamental concepts - asymptotic responses, group delay, phase delay, etc. There is a brief introduction to cepstrology, with emphasis on acoustical applications. The treatment of the mathematical properties of noise emphasizes the generation of different kinds of noise. Digital signal processing with sampled data is specifically introduced with emphasis on digital-to-analog conversion and analog-to-digital conversion. It continues with the discrete Fourier transform and with the -transform, applied to both signals and linear, time-invariant systems. Digital signal processing continues with an introduction to maximum length sequences as used in acoustical measurements, with an emphasis on formal properties. The chapter ends with a section on information theory including developments of Shannon entropy and mutual information.

This chapter provides an introduction to the physical and psycho-acoustic principles underlying the production and perception of the sounds of musical instruments. The first section introduces generic aspects of musical acoustics and the perception of musical sounds, followed by separate sections on string, wind and percussion instruments.

In all sections, we start by considering the vibrations of simple systems – like stretched strings, simple air columns, stretched membranes, thin plates and shells. We show that, for almost all musical instruments, the usual text-book description of such systems is strongly perturbed by material properties, geometrical factors and acoustical coupling between the drive mechanism, vibrating system and radiated sound.

For stringed, woodwind and brass instruments, we discuss excitation by the bow, reed and vibrating lips, which all involve strongly non-linear processes, even though the vibrations of the excited system usually remains well within the linear regime. However, the amplitudes of vibration of very strongly excited strings, air columns, thin plates and membranes can sometimes exceed the linear approximation limit, resulting in a number of interesting non-linear phenomena, often of significant musical importance.

Musical acoustics therefore provides an excellent introduction to the physics of both linear and non-linear acoustical systems, in a context of rather general interest to professional acousticians, teachers and students, at both school and college levels.

The subject continues its long tradition in advancing the frontiers of experimental, computational and theoretical acoustics, in an area of wide general appeal and contemporary relevance.

By discussing the theoretical models and experimental methods used to investigate the acoustics of many musical instruments, we have aimed to provide a useful background for professional acousticians, students and their teachers, for whom musical acoustics provides an exceedingly rich area for original research projects at all educational levels.

Because the subject is ultimately about the sounds produced by musical instruments, a large number of audio illustrations have been provided on a CD accompanying this volume, which can also be accessed by the electronic version of the Handbook on . The extensive list of references is intended as a useful starting point for entry to the current research literature, but makes no attempt to provide a comprehensive list of all important research.

This chapter highlights the acoustics of musical instruments. Other related topics, such as the human voice, the perception and psychology of sound, architectural acoustics, sound recording and reproduction, and many experimental, computational and analytic techniques are described in more detail elsewhere in this volume.

This chapter describes various aspects of the human voice as a means of communication in speech and singing. From the point of view of function, vocal sounds can be regarded as the end result of a three stage process: (1) the compression of air in the respiratory system, which produces an exhalatory airstream, (2) the vibrating vocal foldsʼ transformation of this air stream to an intermittent or pulsating air stream, which is a complex tone, referred to as the voice source, and (3) the filtering of this complex tone in the vocal tract resonator. The main function of the respiratory system is to generate an overpressure of air under the glottis, or a subglottal pressure. Section  describes different aspects of the respiratory system of significance to speech and singing, including lung volume ranges, subglottal pressures, and how this pressure is affected by the ever-varying recoil forces. The complex tone generated when the air stream from the lungs passes the vibrating vocal folds can be varied in at least three dimensions: fundamental frequency, amplitude and spectrum. Section  describes how these properties of the voice source are affected by the subglottal pressure, the length and stiffness of the vocal folds and how firmly the vocal folds are adducted. Section  gives an account of the vocal tract filter, how its form determines the frequencies of its resonances, and Sect.  gives an account for how these resonance frequencies or formants shape the vocal sounds by imposing spectrum peaks separated by spectrum valleys, and how the frequencies of these peaks determine vowel and voice qualities. The remaining sections of the chapter describe various aspects of the acoustic signals used for vocal communication in speech and singing. The syllable structure is discussed in Sect. , the closely related aspects of rhythmicity and timing in speech and singing is described in Sect. , and pitch and rhythm aspects in Sect. . The impressive control of all these acoustic characteristics of vocal signals is discussed in Sect. , while Sect.  considers expressive aspects of vocal communication.

This chapter covers algorithms, technologies, computer languages, and systems for computer music. Computer music involves the application of computers and other digital/electronic technologies to music composition, performance, theory, history, and perception. The field combines digital signal processing, computational algorithms, computer languages, hardware and software systems, acoustics, psychoacoustics (low-level perception of sounds from the raw acoustic signal), and music cognition (higher-level perception of musical style, form, emotion, etc.). Although most people would think that analog synthesizers and electronic music substantially predate the use of computers in music, many experiments and complete computer music systems were being constructed and used as early as the 1950s.

Because of this rich legacy, and the large number of researchers working on digital audio (primarily in speech research laboratories), there are a large number of algorithms for synthesizing sound using computers. Thus, a significant emphasis in this chapter will be placed on digital sound synthesis and processing, first providing an overview of the representation of audio in digital systems, then covering most of the popular algorithms for digital analysis and synthesis of sound.

This chapter surveys devices and systems associated with audio and electroacoustics: the acquisition, transmission, storage, and reproduction of audio. The chapter provides an historical overview of the field since before the days of Edison and Bell to the present day, and analyzes performance of audio transducers, components and systems from basic psychoacoustic principles, to arrive at an assessment of the perceptual performance of such elements and an indication of possible directions for future progress.

The first, introductory section is an overall historical review of audio reproduction and spatial audio to establish the context of events. The next section surveys relevant psychoacoustic principles, including performance related to frequency response, amplitude, timing, and spatial acuity. Section 3 examines common audio specifications, with reference to the psychoacoustic limitations discussed in Sect. 2. The specifications include frequency and phase response, distortion, noise, dynamic range and speed accuracy. Section 4 examines some of the common audio components in light of the psychoacoustics and specifications established in the preceding sections. The components in question include microphones, loudspeakers, record players, amplifiers, magnetic recorders, radio, and optical media. Section 5 is concerned with digital audio, including the basics of sampling, digital signal processing, and audio coding. Section 6 is devoted to an examination of complete audio systems and their ability to reproduce an arbitrary acoustic environment. The specific systems include monaural, stereo, binaural, Ambisonics, and 5.1-channel surround sound. The final section provides an overall appraisal of the current state of audio and electroacoustics, and speculates on possible future directions for research and development.

Animals rely upon their acoustic and vibrational senses and abilities to detect the presence of both predators and prey and to communicate with members of the same species. This chapter surveys the physical bases of these abilities and their evolutionary optimization in insects, birds, and other land animals, and in a variety of aquatic animals other than cetaceans, which are treated in Chap. 20. While there are many individual variations, and some animals devote an immense fraction of their time and energy to acoustic communication, there are also many common features in their sound production and in the detection of sounds and vibrations. Excellent treatments of these matters from a biological viewpoint are given in several notable books [,] and collections of papers [,,,,,], together with other more specialized books to be mentioned in the following sections, but treatments from an acoustical viewpoint [] are rare. The main difference between these two approaches is that biological books tend to concentrate on anatomical and physiological details and on behavioral outcomes, while acoustical books use simplified anatomical models and quantitative analysis to model whole-system behavior. This latter is the approach to be adopted here.

The mammalian order cetacea consist of dolphins and whales, animals that are found in all the oceans and seas of the world. A few species even inhabit fresh water lakes and rivers. A list of 80 species of cetaceans in a convenient table is presented by  []. These mammals vary considerably in size, from the largest living mammal, the large blue whale (), to the very small harbor porpoise () and Commersonʼs dolphin (), which are typically slightly over a meter in length.

Cetaceans are subdivided into two suborders, odontoceti and mysticeti. Odontocetes are the toothed whales and dolphins, the largest being the sperm whale (), followed by the Bairdʼs beaked whale () and the killer whale (). Within the suborder odontoceti there are four superfamilies: , , , and . Over half of all cetaceans belong to the superfamily , consisting of seven species of medium whales and 35 species of small whales also known as dolphins and porpoises []. Dolphins generally have a sickle-shaped dorsal fin, conical teeth, and a long rostrum. Porpoises have a more triangular dorsal fin, more spade-shaped teeth, and a much shorter rostrum [].

Mysticetes are toothless, and in the place of teeth they have rigid brush-like whalebone plate material called baleen hanging from their upper jaw. The baleen is used to strain shrimp, krill, micronekton, and zooplankton. All the great whales are mysticetes or baleen whales and all are quite large. The sperm and Bairds beaked whales are the only odontocetes that are larger than the smaller mysticetes such as Minke whales and pygmy right whales. Baleen whales are subdivided into four families, (right and bowhead whales), (gray whales), (Minke, sei, Brydeʼs, blue, fin, and humpback whales), and (pygmy right whale).

Acoustics play a large role in the lives of cetaceans since sound travels underwater better than any other form of energy. Vision underwater is limited to tens of meters under the best conditions and less than a fraction of a meter in turbid and murky waters. Visibility is also limited by the lack of light at great depths during the day and at almost any depth on a moonless night. Sounds are used by marine mammals for myriad reasons such as group cohesion, group coordination, communications, mate selection, navigation and locating food. Sound is also used over different spatial scales from tens of km for some species and tens of meters for other species, emphasizing the fact that different species utilize sound in different ways. All odontocetes seem to have the capability to echolocate, while mysticetes do not echolocate except in a very broad sense, such as listening to their sound bouncing off the bottom, sea mounts, underwater canyon walls, and other large objects.

The general rule of thumb is that larger animals tend to emit lower-frequency sounds and the frequency range utilized by a specific species may be dictated more from anatomical constraints than any other factors. If resonance is involved with sound production, then anatomical dimensions become critical, that is, larger volumes resonate at lower frequencies than smaller volumes. The use of a particular frequency band will also have implications as to the distance other animals, including conspecifics, will be able to hear the sounds. Acoustic energy is lost in the propagation process by geometric spreading and absorption. Absorption losses are frequency dependent, increasing with frequency. Therefore, the sounds of baleen whales such as the blue whale that emit sounds with fundamental frequencies as low as 15 Hz can propagate to much longer distances than the whistles of dolphins that contain frequencies between 5 and 25 kHz.