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Related Concept Videos

Design Example01:23

Design Example

The innovation of touch-tone telephony revolutionized the telecommunications industry by replacing the traditional rotary dial with a dual-tone multi-frequency (DTMF) signaling system. This system uses a matrix-style keypad with buttons arranged in four rows and three columns, creating 12 distinct signals each assigned to a pair of frequencies. Each button press results in a simultaneous generation of two sinusoidal tones – one from a low-frequency group (697 to 941 Hz) and one from a...
Passive Filters01:27

Passive Filters

Passive filters are utilized to shape the frequency spectrum of signals across a diverse array of applications. These filters, using only passive elements like resistors (R), inductors (L), and capacitors (C), are capable of selectively allowing or blocking certain frequency ranges without the need for external power sources.
Low-Pass Filters
Low-pass filters are designed to transmit signals with frequencies lower than the cutoff frequency, ωc, and attenuate those above it. The cutoff frequency...
Perceiving Loudness, Pitch, and Location01:21

Perceiving Loudness, Pitch, and Location

The human brain perceives pitch through two primary mechanisms reflected in place theory and frequency theory. Each mechanism describes how sound waves are interpreted as specific pitches by the brain, offering insights into the intricate processes of auditory perception.
Place theory, or place coding, suggests that different pitches are heard because various sound waves activate specific locations along the cochlea's basilar membrane. The brain determines the pitch of a sound by identifying...
Sound Intensity00:58

Sound Intensity

The loudness of a sound source is related to how energetically the source is vibrating, consequently making the molecules of the propagation medium vibrate. To measure the loudness of a source, the physical quantity of interest is the intensity. This is defined as the energy emitted per unit of time per unit of area perpendicular to the sound wave's propagation direction. Since the total energy is greater if the source vibrates for a longer duration and over a larger area, dividing the emitted...
Sound Waves: Resonance01:14

Sound Waves: Resonance

Resonance is produced depending on the boundary conditions imposed on a wave. Resonance can be produced in a string under tension with symmetrical boundary conditions (i.e., has a node at each end). A node is defined as a fixed point where the string does not move. The symmetrical boundary conditions result in some frequencies resonating and producing standing waves, while other frequencies interfere destructively. Sound waves can resonate in a hollow tube, and the frequencies of the sound...
Sound Waves: Interference00:53

Sound Waves: Interference

Sound waves can be modeled either as longitudinal waves, wherein the molecules of the medium oscillate around an equilibrium position, or as pressure waves. When two identical waves from the same source superimpose on each other, the combination of two crests or two troughs results in amplitude reinforcement known as constructive interference. If two identical waves, that are initially in phase, become out of phase because of different path lengths, the combination of crests with troughs...

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Related Experiment Video

Updated: Jun 3, 2026

Sound Source Localization Testing in Single-sided Deafness Following Bone Conduction Intervention
04:32

Sound Source Localization Testing in Single-sided Deafness Following Bone Conduction Intervention

Published on: December 20, 2024

Sound reproduction systems using variable-directivity loudspeakers.

M A Poletti1, F M Fazi, P A Nelson

  • 1Industrial Research Ltd., P.O. Box 31-310, Lower Hutt, New Zealand. m.poletti@irl.cri.nz

The Journal of the Acoustical Society of America
|March 25, 2011
PubMed
Summary
This summary is machine-generated.

Variable-directivity loudspeakers effectively eliminate unwanted sound reflections at low frequencies, significantly improving audio quality in multi-channel systems. This research offers insights for designing better commercial sound reproduction technologies.

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A Method to Study Adaptation to Left-Right Reversed Audition
07:14

A Method to Study Adaptation to Left-Right Reversed Audition

Published on: October 29, 2018

Area of Science:

  • Acoustics
  • Audio Engineering
  • Signal Processing

Background:

  • Omnidirectional loudspeakers create interfering sound reflections from room surfaces.
  • Active compensation systems for reverberation are complex and require room-specific calibration.
  • Directional loudspeakers improve direct-to-reverberant sound ratios but still produce external sound fields.

Purpose of the Study:

  • To investigate the performance of variable-directivity loudspeaker arrays in reducing reverberant sound levels.
  • To compare the effectiveness of variable-directivity arrays against fixed-directivity arrays.
  • To explore the application of the Kirchhoff-Helmholtz integral equation for controlling sound fields.

Main Methods:

  • Implementing the Kirchhoff-Helmholtz integral equation to control loudspeaker directivity.
  • Utilizing variable-directivity loudspeaker arrays.
  • Comparing performance metrics with previously studied fixed-directivity arrays.

Main Results:

  • Variable-directivity loudspeakers can eliminate the exterior sound field at low frequencies.
  • Significant reduction in reverberant sound levels was achieved using variable-directivity arrays.
  • Performance was evaluated in terms of direct-to-reverberant sound levels and overall sound field control.

Conclusions:

  • Variable-directivity loudspeaker arrays offer a promising method for reducing reverberation without complex calibration.
  • The findings suggest a potential impact on the design of future commercial multi-channel sound reproduction systems.
  • Eliminating the exterior field at low frequencies is key to improving sound reproduction fidelity in enclosed spaces.