A white noise machine is a device that produces a noise that calms the listener, which in many cases sounds like a rushing waterfall or wind blowing through trees, and other serene or nature-like sounds. Often such devices do not produce actual white noise, which has a harsh sound, but pink noise, whose power rolls off at higher frequencies, or other colors of noise.
White noise devices are available from numerous manufacturers in many forms, for a variety of different uses, including audio testing, sound masking, sleep-aid, and power-napping. Sleep-aid and nap machine products may also produce other soothing sounds, such as music, rain, wind, highway traffic and ocean waves mixed with—or modulated by—white noise. Electric fans are a common alternative, although some Asian communities historically avoided using fans due to the superstition that a fan could suffocate them while sleeping. [1] [2] [3] [4] White noise generators are often used by people with tinnitus to mask their symptoms. The sounds generated by digital machines are not always truly random. Rather, they are short prerecorded audio-tracks which continuously repeat at the end of the track.
Manufacturers of sound-masking devices recommend that the volume of white noise machines be initially set at a comfortable level, even if it does not provide the desired level of privacy. As the ear becomes accustomed to the new sound and learns to tune it out, the volume can be gradually increased to increase privacy. Manufacturers of sleeping aids and power-napping devices recommend that the volume level be set slightly louder than normal music listening level, but always in a comfortable listening range.
Sound and noise have their own measurement and color coding techniques, which allows specialized users to identify noise and sound according to their respective needs and utilization. These specialized needs are dependent on certain professions and needs, e.g. a psychiatrist who needs certain sounds for therapies and treatments on a mental level, and patients who have conditions such as insomnia, anxiety, and, tinnitus (these conditions are managed with special devices which are designed to create certain sounds that treat such conditions at a mental level). A white noise machine has “white” as the color code given to that noise having a particular frequency spectrum.
White noise machines are used to diminish the potential for recording or overhearing conversations. Republican Glen Casada had a white noise machine installed in his office to prevent against eavesdropping. [5]
Smart speaker blockers have been developed. For example, Bracelet of Silence is a bracelet that outputs white noise to protect privacy against digital recording from smart speakers. [6] Bracelet of Silence is portable and not attached to smart speakers, thus it is possible that this device can be used to prevent eavesdropping of other devices as well, for example smartphones and laptops.
There is not a lot of research on the impact of loud sounds at inaudible frequencies (and their respective audible artifacts and harmonics). [7]
Most modern white noise generators are electronic, usually generating the sound in real-time with audio test equipment, or via electronic playback of a digital audio recording. Simple mechanical machines consist of a very basic setup, involving an enclosed fan and, optionally, a speed switch. This fan drives air through small slots in the machine's casing, producing the desired sound. The first fan-based white noise machine was the Marpac Dohm, [8] which was invented in 1962 and is frequently credited as the original domestic use white noise machine.
One paper found that of the 14 white noise machines tested at maximum volume, all exceeded maximum safe sound levels for infants (50 dB). Three exceeded safe levels for adults (85 dB). [9]
In signal processing, white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. The term is used, with this or similar meanings, in many scientific and technical disciplines, including physics, acoustical engineering, telecommunications, and statistical forecasting. White noise refers to a statistical model for signals and signal sources, rather than to any specific signal. White noise draws its name from white light, although light that appears white generally does not have a flat power spectral density over the visible band.
A covert listening device, more commonly known as a bug or a wire, is usually a combination of a miniature radio transmitter with a microphone. The use of bugs, called bugging, or wiretapping is a common technique in surveillance, espionage and police investigations.
Audio feedback is a positive feedback situation which may occur when an acoustic path exists between an audio input and an audio output. In this example, a signal received by the microphone is amplified and passed out of the loudspeaker. The sound from the loudspeaker can then be received by the microphone again, amplified further, and then passed out through the loudspeaker again. The frequency of the resulting howl is determined by resonance frequencies in the microphone, amplifier, and loudspeaker, the acoustics of the room, the directional pick-up and emission patterns of the microphone and loudspeaker, and the distance between them. The principles of audio feedback were first discovered by Danish scientist Søren Absalon Larsen, hence it is also known as the Larsen effect.
Home cinema, also called home theaters or theater rooms, are home entertainment audio-visual systems that seek to reproduce a movie theater experience and mood using consumer electronics-grade video and audio equipment that is set up in a room or backyard of a private home. Some studies show films are rated better and generate more intense emotions when watched in a movie theater, however, convenience is a major appeal for home cinemas. In the 1980s, home cinemas typically consisted of a movie pre-recorded on a LaserDisc or VHS tape; a LaserDisc Player or VCR; and a heavy, bulky large-screen cathode ray tube TV set, although sometimes CRT projectors were used instead. In the 2000s, technological innovations in sound systems, video player equipment and TV screens and video projectors have changed the equipment used in home cinema set-ups and enabled home users to experience a higher-resolution screen image, improved sound quality and components that offer users more options. The development of Internet-based subscription services means that 2016-era home theatre users do not have to commute to a video rental store as was common in the 1980s and 1990s
Active noise control (ANC), also known as noise cancellation (NC), or active noise reduction (ANR), is a method for reducing unwanted sound by the addition of a second sound specifically designed to cancel the first. The concept was first developed in the late 1930s; later developmental work that began in the 1950s eventually resulted in commercial airline headsets with the technology becoming available in the late 1980s. The technology is also used in road vehicles, mobile telephones, earbuds, and headphones.
A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss. Hearing aids are classified as medical devices in most countries, and regulated by the respective regulations. Small audio amplifiers such as personal sound amplification products (PSAPs) or other plain sound reinforcing systems cannot be sold as "hearing aids".
A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers in enclosures all controlled by a mixing console that makes live or pre-recorded sounds louder and may also distribute those sounds to a larger or more distant audience. In many situations, a sound reinforcement system is also used to enhance or alter the sound of the sources on the stage, typically by using electronic effects, such as reverb, as opposed to simply amplifying the sources unaltered.
A cordless telephone or portable telephone has a portable telephone handset that connects by radio to a base station connected to the public telephone network. The operational range is limited, usually to the same building or within some short distance from the base station.
An earplug is a device that is inserted in the ear canal to protect the user's ears from loud noises, intrusion of water, foreign bodies, dust or excessive wind. Since they reduce the sound volume, earplugs are often used to help prevent hearing loss and tinnitus.
An equal-loudness contour is a measure of sound pressure level, over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. The unit of measurement for loudness levels is the phon and is arrived at by reference to equal-loudness contours. By definition, two sine waves of differing frequencies are said to have equal-loudness level measured in phons if they are perceived as equally loud by the average young person without significant hearing impairment.
Earmuffs are clothing accessories or personal protective equipment designed to cover a person's ears for hearing protection or warmth. They consist of a thermoplastic or metal head-band that fits over the top or back of the head, and a cushion or cup at each end to cover the ears.
Tinnitus retraining therapy (TRT) is a form of habituation therapy designed to help people who experience tinnitus—a ringing, buzzing, hissing, or other sound heard when no external sound source is present. Two key components of TRT directly follow from the neurophysiological model of tinnitus: Directive counseling aims to help the sufferer reclassify tinnitus to a category of neutral signals, and sound therapy weakens tinnitus-related neuronal activity.
Comfort noise is synthetic background noise used in radio and wireless communications to fill the artificial silence in a transmission resulting from voice activity detection or from the audio clarity of modern digital lines.
Noise health effects are the physical and psychological health consequences of regular exposure to consistent elevated sound levels. Noise from traffic, in particular, is considered by the World Health Organization to be one of the worst environmental stressors for humans, second only to air pollution. Elevated workplace or environmental noise can cause hearing impairment, tinnitus, hypertension, ischemic heart disease, annoyance, and sleep disturbance. Changes in the immune system and birth defects have been also attributed to noise exposure.
A wireless microphone, or cordless microphone, is a microphone without a physical cable connecting it directly to the sound recording or amplifying equipment with which it is associated. Also known as a radio microphone, it has a small, battery-powered radio transmitter in the microphone body, which transmits the audio signal from the microphone by radio waves to a nearby receiver unit, which recovers the audio. The other audio equipment is connected to the receiver unit by cable. In one type the transmitter is contained within the handheld microphone body. In another type the transmitter is contained within a separate unit called a "bodypack", usually clipped to the user's belt or concealed under their clothes. The bodypack is connected by wire to a "lavalier microphone" or "lav", a headset or earset microphone, or another wired microphone. Most bodypack designs also support a wired instrument connection. Wireless microphones are widely used in the entertainment industry, television broadcasting, and public speaking to allow public speakers, interviewers, performers, and entertainers to move about freely while using a microphone without requiring a cable attached to the microphone.
Sound masking is the inclusion of generated sound into an environment to mask unwanted sound. It relies on auditory masking. Sound masking is not a form of active noise control ; however, it can reduce or eliminate the perception of sound. Sound masking is applied to an entire area to improve acoustical satisfaction, thus improving the acoustical privacy of the space. This can help an individual focus and thereby enhance productivity.
A speaker pillow is a pillow that incorporates loudspeakers. It is generally designed as an alternative to headphones connected to portable media players.
Wireless speakers are loudspeakers that receive audio signals using radio frequency (RF) waves rather than over audio cables. The two most popular RF frequencies that support audio transmission to wireless loudspeakers include a variation of WiFi IEEE 802.11, while others depend on Bluetooth to transmit audio data to the receiving speaker.
Tinnitus maskers are a range of devices based on simple white noise machines used to add natural or artificial sound into a tinnitus sufferer's environment in order to mask or cover up the ringing. The noise is supplied by a sound generator, which may reside in or above the ear or be placed on a table or elsewhere in the environment. The noise is usually white noise or music, but in some cases, it may be patterned sound or specially tailored sound based on the characteristics of the person's tinnitus.