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Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics technology may be called an acoustical engineer. The application of acoustics is present in almost all aspects of modern society with the most obvious being the audio and noise control industries.
Spectroscopy is the study of the interaction between matter and electromagnetic radiation as a function of the wavelength or frequency of the radiation. In simpler terms, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum; indeed, historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a prism. Matter waves and acoustic waves can also be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO).
The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the inner ear. The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear is also known as the tympanic cavity and is surrounded by the tympanic part of the temporal bone. The auditory tube joins the tympanic cavity with the nasal cavity (nasopharynx), allowing pressure to equalize between the middle ear and throat.
A microphone, colloquially called a mic or mike, is a device – a transducer – that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, sound recording, two-way radios, megaphones, radio and television broadcasting. They are also used in computers for recording voice, speech recognition, VoIP, and for non-acoustic purposes such as ultrasonic sensors or knock sensors.
Skeletal muscles are organs of the vertebrate muscular system that are mostly attached by tendons to bones of the skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle tissue, and are often known as muscle fibers. The muscle tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres.
Bioacoustics is a cross-disciplinary science that combines biology and acoustics. Usually it refers to the investigation of sound production, dispersion and reception in animals. This involves neurophysiological and anatomical basis of sound production and detection, and relation of acoustic signals to the medium they disperse through. The findings provide clues about the evolution of acoustic mechanisms, and from that, the evolution of animals that employ them.
Muscle fatigue is the decline in ability of muscles to generate force. It can be a result of vigorous exercise but abnormal fatigue may be caused by barriers to or interference with the different stages of muscle contraction. There are two main causes of muscle fatigue: the limitations of a nerve’s ability to generate a sustained signal ; and the reduced ability of the muscle fiber to contract.
Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyograph detects the electric potential generated by muscle cells when these cells are electrically or neurologically activated. The signals can be analyzed to detect abnormalities, activation level, or recruitment order, or to analyze the biomechanics of human or animal movement. Needle EMG is an electrodiagnostic medicine technique commonly used by neurologists. Surface EMG is a non-medical procedure used to assess muscle activation by several professionals, including physiotherapists, kinesiologists and biomedical engineers. In Computer Science, EMG is also used as middleware in gesture recognition towards allowing the input of physical action to a computer as a form of human-computer interaction.
The acoustic reflex is an involuntary muscle contraction that occurs in the middle ear in response to loud sound stimuli or when the person starts to vocalize.
The tensor tympani is a muscle within the middle ear, located in the bony canal above the bony part of the auditory tube, and connects to the malleus bone. Its role is to dampen loud sounds, such as those produced from chewing, shouting, or thunder. Because its reaction time is not fast enough, the muscle cannot protect against hearing damage caused by sudden loud sounds, like explosions or gunshots.
A biosignal is any signal in living beings that can be continually measured and monitored. The term biosignal is often used to refer to bioelectrical signals, but it may refer to both electrical and non-electrical signals. The usual understanding is to refer only to time-varying signals, although spatial parameter variations are sometimes subsumed as well.
Analysis of sound and acoustics plays a role in such engineering tasks as product design, production test, machine performance, and process control. For instance, product design can require modification of sound level or noise for compliance with standards from ANSI, IEC, and ISO. The work might also involve design fine-tuning to meet market expectations. Here, examples include tweaking an automobile door latching mechanism to impress a consumer with a satisfying click or modifying an exhaust manifold to change the tone of an engine's rumble. Aircraft designers are also using acoustic instrumentation to reduce the noise generated on takeoff and landing.
Noise, vibration, and harshness (NVH), also known as noise and vibration (N&V), is the study and modification of the noise and vibration characteristics of vehicles, particularly cars and trucks. While noise and vibration can be readily measured, harshness is a subjective quality, and is measured either via jury evaluations, or with analytical tools that can provide results reflecting human subjective impressions. The latter tools belong to the field psychoacoustics.
Phonomyography (PMG) is a technique to measure the force of muscle contraction by recording the low frequency sounds created during muscular activity.
Ultrasonic transducers and ultrasonic sensors are devices that generate or sense ultrasound energy. They can be divided into three broad categories: transmitters, receivers and transceivers. Transmitters convert electrical signals into ultrasound, receivers convert ultrasound into electrical signals, and transceivers can both transmit and receive ultrasound.
Brüel & Kjær is a Danish multinational engineering and electronics company headquartered in Nærum, near Copenhagen. It is the world's largest manufacturer and supplier of sound and vibration measurement equipment, systems and solutions. Brüel & Kjær is a subsidiary of Spectris.
Magnetomyography (MMG) is a technique for mapping muscle activity by recording magnetic fields produced by electrical currents occurring naturally in the muscles, using arrays of SQUIDs. It has a better capability than electromyography for detecting slow or direct currents. The magnitude of the MMG signal is in the scale of pico (10−12) to femto (10−15) Tesla (T). Miniaturizing MMG offers a prospect to modernize the bulky SQUID to wearable miniaturized magnetic sensors.
Increased intracranial pressure (ICP) is one of the major causes of secondary brain ischemia that accompanies a variety of pathological conditions, most notably traumatic brain injury (TBI), strokes, and intracranial hemorrhages. It can cause complications such as vision impairment due to intracranial pressure (VIIP), permanent neurological problems, reversible neurological problems, seizures, stroke, and death. However, aside from a few Level I trauma centers, ICP monitoring is rarely a part of the clinical management of patients with these conditions. The infrequency of ICP can be attributed to the invasive nature of the standard monitoring methods. Additional risks presented to patients can include high costs associated with an ICP sensor's implantation procedure, and the limited access to trained personnel, e.g. a neurosurgeon. Alternative, non-invasive measurement of intracranial pressure, non-invasive methods for estimating ICP have, as a result, been sought.
Optomyography (OMG) was proposed in 2015 as a technique that could be used to monitor muscular activity. It is possible to use OMG for the same applications where Electromyography (EMG) and Mechanomyography (MMG) are used. However, OMG offers superior signal-to-noise ratio and improved robustness against the disturbing factors and limitations of EMG and MMG. The basic principle of OMG is to use active near-infra-red optical sensors to measure the variations in the measured signals that are reflected from the surface of the skin while activating the muscles below and around the skin spot where the photoelectric sensor is focusing to measure the signals reflected from this spot.
Robotic prosthesis control is a method for controlling a prosthesis in such a way that the controlled robotic prosthesis restores a biologically accurate gait to a person with a loss of limb. This is a special branch of control that has an emphasis on the interaction between humans and robotics.
References
- ↑ Beck TW, Housh TJ, Cramer JT, Weir JP, Johnson GO, Coburn JW, et al. (December 2005). "Mechanomyographic amplitude and frequency responses during dynamic muscle actions: a comprehensive review". BioMedical Engineering Online. 4: 67. doi:10.1186/1475-925X-4-67. PMC 1343566 . PMID 16364182.
- ↑ Krasoulis A, Kyranou I, Erden MS, Nazarpour K, Vijayakumar S (July 2017). "Improved prosthetic hand control with concurrent use of myoelectric and inertial measurements". Journal of Neuroengineering and Rehabilitation. 14 (1): 71. doi:10.1186/s12984-017-0284-4. PMC 5505040 . PMID 28697795.
- ↑ Grimaldi FM (1665). Physico-mathesis de lumine, coloribus, et iride, aliisque adnexis libri duo. Bologna. p. 383.
- ↑ Wollaston WH (1810). "On the duration of muscle action". Philosophical Transactions of the Royal Society of London. 100: 1–5. doi: 10.1098/rstl.1810.0002 .
- ↑ Erman, P (1812). "Einige Bemerkungen uber Muscular-Contraction". Annalen der Physik. 40 (1): 1–30. Bibcode:1812AnP....40....1E. doi:10.1002/andp.18120400102.
- ↑ Stokes M, Blythe M (2001). Muscle Sounds in physiology, sports science and clinical investigation. Oxford: Medintel. ISBN 978-0-9540572-0-6.