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In the field of
acoustics Acoustics is a branch of physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, in other wo ...
, a diaphragm is a
transducer A transducer is a device that energy from one form to another. Usually a transducer converts a in one form of energy to a signal in another. Transducers are often employed at the boundaries of , , and s, where electrical signals are converted t ...

transducer
intended to inter-convert mechanical vibrations to sounds, or vice versa. It is commonly constructed of a thin membrane or sheet of various materials, suspended at its edges. The varying air pressure of sound waves imparts mechanical vibrations to the diaphragm which can then be converted to some other type of signal; examples of this type of diaphragm are found in
microphone A microphone, colloquially called a mic or mike (), is a device – a transducer – that converts sound In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''ph ...

microphone
s and the human
eardrum In the anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is a ...
. Conversely a diaphragm vibrated by a source of energy beats against the air, creating sound waves. Examples of this type of diaphragm are
loudspeaker A loudspeaker (or ''speaker driver'', or most frequently just ''speaker'') is an Acoustical engineering#Electroacoustics, electroacoustic transducer, that is, a device that converts an electrical audio signal into a corresponding sound. A ''spe ...

loudspeaker
cones and
earphone Headphones are a pair of small Electrodynamic speaker driver, loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustics (acoustical engineering), electroacoustic transducers, which convert an electrical sign ...

earphone
diaphragms and are found in
air horn , in Merseyside Maritime Museum, UK An air horn is a pneumatic device designed to create an extremely loud noise for signaling purposes. It usually consists of a source which produces compressed air Compressed air is air File:Atmosphere g ...
s.


Loudspeaker

In a dynamic
loudspeaker A loudspeaker (or ''speaker driver'', or most frequently just ''speaker'') is an Acoustical engineering#Electroacoustics, electroacoustic transducer, that is, a device that converts an electrical audio signal into a corresponding sound. A ''spe ...

loudspeaker
, a diaphragm is the thin, semi-rigid
membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Biological membranes include cell membranes (outer coverings of cells or organelles that all ...
attached to the
voice coil A voice coil (consisting of a bobbin, former, Collar (clothing), collar, and winding) is the coil of wire attached to the apex of a speaker driver, loudspeaker cone. It provides the motive force to the cone by the reaction of a magnetic field to ...
, which moves in a magnetic gap, vibrating the diaphragm, and producing
sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the b ...

sound
. It can also be called a cone, though not all speaker diaphragms are cone-shaped. Diaphragms are also found in
headphones Headphones are a pair of small Electrodynamic speaker driver, loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustics (acoustical engineering), electroacoustic transducers, which convert an electrical sign ...

headphones
. Quality midrange and bass drivers are usually made from paper, paper composites and laminates, plastic materials such as
polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic A thermoplastic, or thermosoftening plastic, is a plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most the ...

polypropylene
, or mineral/fiber filled polypropylene. Such materials have very high strength/weight ratios (paper being even higher than metals) and tend to be relatively immune from flexing during large excursions. This allows the driver to react quickly during transitions in music (i.e. fast changing transient impulses) and minimizes acoustical output distortion. If properly designed in terms of mass, stiffness, and damping, paper woofer/midrange cones can outperform many exotic drivers made from more expensive materials. Other materials used for diaphragms include
polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic A thermoplastic, or thermosoftening plastic, is a plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most the ...

polypropylene
(PP), polyetheretherketone (PEEK)
polycarbonate Polycarbonates (PC) are a group of thermoplastic A thermoplastic, or thermosoft plastic, is a plastic polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material co ...

polycarbonate
(PC),
Mylar Metallized boPET film, 32 layers of ~14 µm thickness each BoPET (biaxially-oriented polyethylene terephthalate) is a polyester Polyester is a category of polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, - ...
(PET),
silk Silk is a natural fiber, natural protein fiber, some forms of which can be weaving, woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoon (silk), cocoons. The be ...

silk
, glassfibre,
carbon fibre Carbon fiber reinforced polymer (American English), Carbon fibre reinforced polymer (English in the Commonwealth of Nations, Commonwealth English), or carbon fiber reinforced plastic, or carbon fiber reinforced thermoplastic (CFRP, CRP, CFRTP, ...
,
titanium Titanium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical ele ...

titanium
,
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
, aluminium-
magnesium Magnesium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

magnesium
alloy,
nickel Nickel is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same nu ...

nickel
, and
beryllium Beryllium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science t ...

beryllium
. A paper woofer with a peak-to-peak excursion of 0.5 inches at 60 Hz undergoes a maximum acceleration of 92 "g"s. Paper-based cones account for approximately 85% of the cones sold worldwide. The ability of paper (cellulose) to be easily modified by chemical or mechanical means gives it a practical processing advantage not found in other common cone materials. The purpose of the cone/surround assembly is to accurately reproduce the voice coil signal waveform. Inaccurate reproduction of the voice coil signal results in acoustical distortion. The ideal for a cone/surround assembly is an extended range of linearity or "pistonic" motion characterized by i) minimal acoustical breakup of the cone material, ii) minimal standing wave patterns in the cone, and iii) linearity of the surrounds force-deflection curve. The cone stiffness/damping plus the surround's linearity/damping play a crucial role in accuracy of the reproduced voice coil signal waveform. This is the crux of high-fidelity stereo. The surround may be resin-treated cloth, resin-treated non-wovens, polymeric foams, or thermoplastic elastomers over-molded onto the cone body. An ideal surround has a linear force-deflection curve with sufficient damping to fully absorb vibrational transmissions from the cone/surround interface, and the "toughness" to withstand long-term vibration-induced fatigue. Sometimes the conical part and the outer surround are molded in one step and are one piece as commonly used for a Guitar speaker. Other types of speakers (such as electrostatic loudspeakers) may use a thin membrane instead of a cone.


Microphone

Microphones A microphone, colloquially called a mic or mike (), is a device – a transducer – that converts sound In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''ph ...

Microphones
can be thought of as speakers in reverse. The sound waves strike the thin diaphragm, causing it to vibrate. Microphone diaphragms, unlike speaker diaphragms, tend to be thin and flexible, since they need to absorb as much sound as possible. In a condenser microphone, the diaphragm is placed in front of a plate and is charged. In a dynamic microphone, the diaphragm is glued to a magnetic coil, similar to the one in a dynamic loudspeaker. (In fact, a dynamic speaker can be used as a rudimentary microphone, and vice versa.) The diaphragm in a microphone works similarly to the human
eardrum In the anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is a ...
.


Other uses

In a
phonograph A phonograph, in its later forms also called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910) or since the 1940s called a record player, is a device for the mechanical recording and reproduction of sound I ...

phonograph
reproducer, the diaphragm is a flat disk of typically
mica Micas ( ) are a group of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs natural ...

mica
or
isinglass Isinglass () is a substance obtained from the dried swim bladders of fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. They form a sister group to the tun ...

isinglass
that converts the mechanical vibration imparted on the buttress from the recorded groove into sound. In the case of
acoustic recording A phonograph disc record (also known as a gramophone disc record, especially in British English British English (BrE) is the standard dialect of the English language English is a West Germanic languages, West Germanic language fi ...
the reproducer converts the sound into the motion of the needle that scribes the groove on the recording media.


See also

*
Acoustic membrane An acoustic membrane is a thin layer that vibrates and is used in acoustics to produce or transfer sound, such as a drum, microphone, or loudspeaker. See also

* Membranophone * Vibrations of a circular membrane Acoustics Sound {{Physi ...


References

{{reflist Acoustics Loudspeakers