Waves In Rooms Research Articles

Dah-You Maa and the many facets of modal density

Maa’s formula for the modal density of a room is known to everyone in acoustics. The wonderful part of it is that it so logical and direct that you don’t have to memorize or look it up - you can simply re-derive it on the spot. When it was published by Maa in 1939, there was a competing formulation by Dick Bolt that had the same volume dependent term, but was quite different in the surface area and edge length terms. But by the time of the landmark paper by Morse and Bolt in 1944 [“Sound waves in rooms”, Rev. Mod. Phys. 16(1) (1944)], Maa’s formula had won and was the relationship cited by Morse and Bolt. The uses of modal density in the response statistics of acoustical spaces and structures for the purposes of estimating impedances, energy flow, and phase statistics have grown as recognition of this fundamental property of resonant systems has grown.

Alvin Lucier’s method for determining the acoustic modes of a room.

Students can learn about standing waves in rooms as they recreate the classic 1970 recording by Lucier, “I Am Sitting in a Room”. In this work, the composer records himself describing the process in which he is engaged. The approximately 1‐min recording of his speech is then played back and re‐recorded in the same acoustic environment (an unspecified room). The recording and playback process is repeated several times; the complete work consists of a sequential playback of each iteration. From an acoustically unremarkable, if slightly reverberant, initial recording, the speech is altered with each iteration as the resonance frequencies of the room are amplified relative to other frequencies. Eventually, intelligibility is lost and all that is heard are the modulated tones comprising the harmonic series. Using only a microphone, a digital recording device, a playback system, and a suitable room, students can reproduce this effect while investigating how the room dimensions, shape, and wall materials affect the final outcome.

The application of boundary integral equation methods to the numerical calculation of transient waves in rooms

The boundary integral equations derived from Kirchhoff’s formula and its normal derivative form are available for the numerical calculation of transient waves in rooms. The two equations are compared in view of the stability and accuracy in the numerical calculation of responses in a rigid cubic room in which rigorous responses can be obtained by the image method. Some source waves and some problems appear in the numerical implementation such as the singular integrals, and the treatment of absorbent surfaces is also investigated. Finally, it is shown that the boundary integral equation method is a powerful tool to obtain transient waves in rooms.

Compliance With Guidelines and 1-Year Mortality in Patients With Acute Myocardial Infarction: A Prospective Study

Room reverberation theory provides a theoretical basis of sound fields in rooms. Room acoustics has been investigated following geometrical acoustics or wave theory analysis. The geometrical approach represented by the reverberation time is useful for the design of acoustic space from the macroscopic perspective of sound space. In contrast, the wave theory approach, such as modal analysis, explores fine structures of sound fields and the distribution of eigenfrequencies. Spatial- and frequency-band averaged behavior of sound waves in rooms can be expressed according to the geometrical acoustics. This chapter derives a hybrid formulation of geometrical and wave theory representations of room reverberation. On the other hand, the linear-system theory can unify the two types of approaches, where impulse responses in rooms can be formulated according to the geometrical acoustics, and modal analysis based on the wave theory gives the frequency responses in the sound fields in rooms. The transfer function is defined by the z−transform for the impulse response of a discrete system's well develop audio-engineering technologies, such as room reverberation simulators or equalizers of the sound transmission path in a room. Decomposition of the transfer function into the minimum-phase and all-pass components forms the theoretical basis for the development of audio engineering on room acoustics. This chapter describes the transfer function in terms of poles and zeros, as well as the frequency characteristics of reverberation in rooms.

The complex image method

The classical image method extends to the case of an impedance boundary condition, and also to the case of reflection from the boundary between two homogeneous media. The latter solution was given by Balth van der Pol in 1935 and the impedance boundary case was included in a 1944 review article on sound waves in rooms by Philip M. Morse and Richard H. Bolt. Unfortunately, these solutions are seldom mentioned in text books on acoustics, and hence these solutions have been rediscovered more than once, and also quite recently. This will be exemplified here by a brief review of the literature. The main result is a simple derivation of the complex image method. The derivation is particularly simple in the case of an impedance boundary condition, but the derivation is valid for reflection of spherical waves from an arbitrary layered medium.

Assessment of the best loading dose of Clopidogree to Blunt Activation, Inflammation, On-going Necrosis (ALBION)

Room reverberation theory provides a theoretical basis of sound fields in rooms. Room acoustics has been investigated following geometrical acoustics or wave theory analysis. The geometrical approach represented by the reverberation time is useful for the design of acoustic space from the macroscopic perspective of sound space. In contrast, the wave theory approach, such as modal analysis, explores fine structures of sound fields and the distribution of eigenfrequencies. Spatial- and frequency-band averaged behavior of sound waves in rooms can be expressed according to the geometrical acoustics. This chapter derives a hybrid formulation of geometrical and wave theory representations of room reverberation. On the other hand, the linear-system theory can unify the two types of approaches, where impulse responses in rooms can be formulated according to the geometrical acoustics, and modal analysis based on the wave theory gives the frequency responses in the sound fields in rooms. The transfer function is defined by the z−transform for the impulse response of a discrete system's well develop audio-engineering technologies, such as room reverberation simulators or equalizers of the sound transmission path in a room. Decomposition of the transfer function into the minimum-phase and all-pass components forms the theoretical basis for the development of audio engineering on room acoustics. This chapter describes the transfer function in terms of poles and zeros, as well as the frequency characteristics of reverberation in rooms.

Long-term Outcome of Transcatheter Secundum-type Atrial Septal Defect Closure Using Amplatzer Septal Occluders

Room reverberation theory provides a theoretical basis of sound fields in rooms. Room acoustics has been investigated following geometrical acoustics or wave theory analysis. The geometrical approach represented by the reverberation time is useful for the design of acoustic space from the macroscopic perspective of sound space. In contrast, the wave theory approach, such as modal analysis, explores fine structures of sound fields and the distribution of eigenfrequencies. Spatial- and frequency-band averaged behavior of sound waves in rooms can be expressed according to the geometrical acoustics. This chapter derives a hybrid formulation of geometrical and wave theory representations of room reverberation. On the other hand, the linear-system theory can unify the two types of approaches, where impulse responses in rooms can be formulated according to the geometrical acoustics, and modal analysis based on the wave theory gives the frequency responses in the sound fields in rooms. The transfer function is defined by the z−transform for the impulse response of a discrete system's well develop audio-engineering technologies, such as room reverberation simulators or equalizers of the sound transmission path in a room. Decomposition of the transfer function into the minimum-phase and all-pass components forms the theoretical basis for the development of audio engineering on room acoustics. This chapter describes the transfer function in terms of poles and zeros, as well as the frequency characteristics of reverberation in rooms.

Richard H. Bolt’s work on theoretical aspects of room acoustics

From about 1940 to 1950 Dick Bolt undertook a number of studies of the transmission of sound in a room. These were mostly theoretical and appear to have had two sources of inspiration: the work of Wente at Bell Laboratories in the 1930s, and Philip Morse’s work on the eigenfunctions and eigenvalues of idealized rooms in the early 1940s. In 1944, the Reviews of Modern Physics published in its April issue a single paper—that of Dick Bolt and Phil Morse, titled ‘‘Sound waves in rooms.’’ This tour de force took the viewpoint that a deterministic calculation of the modes of an idealized room could reveal important features of the acoustics of less ideal spaces. The relations between wall impedance and modal damping for axial, tangential, and oblique modes and the construction of direct fields from modal expansions are worthy of special note. Perturbation analysis is used to couple idealized modes as a first attempt to deal with ‘‘real’’ rooms and the transition to ergodic behavior. This work then led Bolt to a number of studies of the irregularity of spacing of modal resonance frequencies, which had some influence, in turn, on models of modal distributions in Statistical Energy Analysis.

Trap for controlling standing waves in rooms

This invention is an improved bass trap for controlling standing waves in the listening room. It is cylindrical in shape, with a curved diffuser around one half of the length of the cylinder. The interior of the cylinder is divided into two hemi-cylinders, with one hemi-cylinder made of an absorbing material positioned opposite the curved diffuser, and one hemi-cylinder, which is an air cavity, defined by the boundary of the absorbing material on one side and the diffuser on the other. This device features a ported top, with the ports positioned over the air cavity, which allow tuning pipes of varying length and diameter to be inserted, in order to permit further tuning of the device.

直方体空間の波動関数を用いた固体音放射計算に関する検討 : 建築物床版の振動と音響放射に関する研究 その2

The theory in this study is based on Morse's famous treatise "Sound waves in rooms", and it is investigated by'numerical calculation method that this theory is applicable to the calculation of a sound field generated from vibrations of a wall which composes a room of rectangular parallelepiped ; that is, the calculation of structure borne sound of floor slab. The accuracy'of this method is confirmed by the experiments concerning a piston vibration and a transient vibration of the wall.

Sound Waves in Rooms

Sound Waves in Rooms

Sound Waves in Rooms

Sound Waves in Rooms