Ultrasound in the context of Nondestructive testing

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 brain. Only acoustic waves that have frequencies lying between about 20 Hz and 20 kHz, the audio frequency range, elicit an auditory percept in humans. In air at atmospheric pressure, these represent sound waves with wavelengths of 17 meters (56 ft) to 1.7 centimeters (0.67 in). Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges, allowing some to even hear ultrasounds.

In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes:

• electromagnetic radiation consisting of photons, such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation (γ)
• particle radiation consisting of particles of non-zero rest energy, such as alpha radiation (α), beta radiation (β), proton radiation and neutron radiation
• acoustic radiation, such as ultrasound, sound, and seismic waves, all dependent on a physical transmission medium
• gravitational radiation, in the form of gravitational waves, ripples in spacetime

Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles. Ionizing radiation carries more than 10 electron volts (eV), which is enough to ionize atoms and molecules and break chemical bonds. This is an important distinction due to the large difference in harmfulness to living organisms. A common source of ionizing radiation is radioactive materials that emit α, β, or γ radiation, consisting of helium nuclei, electrons or positrons, and photons, respectively. Other sources include X-rays from medical radiography examinations and muons, mesons, positrons, neutrons and other particles that constitute the secondary cosmic rays that are produced after primary cosmic rays interact with Earth's atmosphere.

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.

Hearing is one of the most crucial means of survival in the animal world and speech is one of the most distinctive characteristics of human development and culture. Accordingly, the science of acoustics spreads across many facets of human society—music, medicine, architecture, industrial production, warfare and more. Likewise, animal species such as songbirds and frogs use sound and hearing as a key element of mating rituals or for marking territories. Art, craft, science and technology have provoked one another to advance the whole, as in many other fields of knowledge. Robert Bruce Lindsay's "Wheel of Acoustics" is a well-accepted overview of the various fields in acoustics.

Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on or under the surface of the water, such as other vessels.

"Sonar" can refer to one of two types of technology: passive sonar means listening for the sound made by vessels; active sonar means emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used for robot navigation, and sodar (an upward-looking in-air sonar) is used for atmospheric investigations. The term sonar is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic). The study of underwater sound is known as underwater acoustics or hydroacoustics.

Miscarriage, also known in medical terms as a spontaneous abortion, is an end to pregnancy resulting in the loss and expulsion of an embryo or fetus from the womb before it can survive independently. Miscarriage before 6 weeks of gestation is defined as biochemical loss by ESHRE. Once ultrasound or histological evidence shows that a pregnancy has existed, the term used is clinical miscarriage, which can be "early" (before 12 weeks) or "late" (between 12 and 21 weeks). Spontaneous fetal termination after 20 weeks of gestation is known as a stillbirth. The term miscarriage is sometimes used to refer to all forms of pregnancy loss and pregnancy with abortive outcomes before 20 weeks of gestation.

The most common symptom of a miscarriage is vaginal bleeding, with or without pain. Tissue and clot-like material may leave the uterus and pass through and out of the vagina. Risk factors for miscarriage include being an older parent, previous miscarriage, exposure to tobacco smoke, obesity, diabetes, thyroid problems, and drug or alcohol use. About 80% of miscarriages occur in the first 12 weeks of pregnancy (the first trimester). The underlying cause in about half of cases involves chromosomal abnormalities. Diagnosis of a miscarriage may involve checking to see if the cervix is open or sealed, testing blood levels of human chorionic gonadotropin (hCG), and an ultrasound. Other conditions that can produce similar symptoms include an ectopic pregnancy and implantation bleeding.

Piezoelectricity (/ˌpiːzoʊ-, ˌpiːtsoʊ-, paɪˌiːzoʊ-/, US: /piˌeɪzoʊ-, piˌeɪtsoʊ-/) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress.

The piezoelectric effect results from the linear electromechanical interaction between the mechanical and electrical states in crystalline materials with no inversion symmetry. The piezoelectric effect is a reversible process: materials exhibiting the piezoelectric effect also exhibit the reverse piezoelectric effect, the internal generation of a mechanical strain resulting from an applied electric field. For example, lead zirconate titanate crystals will generate measurable piezoelectricity when their static structure is deformed by about 0.1% of the original dimension. Conversely, those same crystals will change about 0.1% of their static dimension when an external electric field is applied. The inverse piezoelectric effect is used in the production of ultrasound waves.

In politics, a dog whistle is the use of coded or suggestive language in political messaging to garner support from a particular group without provoking opposition. The concept is named after ultrasonic dog whistles, which are audible to dogs but not humans. Dog whistles use language that appears normal to the majority but communicates specific things to intended audiences. They are generally used to convey messages on issues likely to provoke controversy without attracting negative attention.

Stillbirth is typically defined as the death of a fetus at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life. A stillbirth can often result in the feeling of guilt or grief in the mother. The term is in contrast to miscarriage, which is an early pregnancy loss, and sudden infant death syndrome, where the baby dies a short time after being born alive.

Often the cause is unknown. Causes may include pregnancy complications such as pre-eclampsia and birth complications, problems with the placenta or umbilical cord, birth defects, infections such as malaria and syphilis, and poor health in the mother. Risk factors include a mother's age over 35, smoking, drug use, use of assisted reproductive technology, and first pregnancy. Stillbirth may be suspected when no fetal movement is felt. Confirmation is by ultrasound.

Ernest Rutherford, Baron Rutherford of Nelson (30 August 1871 – 19 October 1937), was a New Zealand physicist and chemist who was a pioneering researcher in both atomic and nuclear physics. He has been described as "the father of nuclear physics" and "the greatest experimentalist since Michael Faraday." In 1908, he was awarded the Nobel Prize in Chemistry "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances." He was the first Oceanian Nobel laureate, and the first to perform Nobel-awarded work in Canada.

Rutherford's discoveries include the concept of radioactive half-life, the radioactive element radon, and the differentiation and naming of alpha and beta radiation. Together with Thomas Royds, Rutherford is credited with proving that alpha radiation is composed of helium nuclei. In 1911, he theorised that atoms have their charge concentrated in a very small nucleus. He arrived at this theory through his discovery and interpretation of Rutherford scattering during the gold foil experiment performed by Hans Geiger and Ernest Marsden. In 1912, he invited Niels Bohr to join his lab, leading to the Bohr model of the atom. In 1917, he performed the first artificially induced nuclear reaction by conducting experiments in which nitrogen nuclei were bombarded with alpha particles. These experiments led him to discover the emission of a subatomic particle that he initially called the "hydrogen atom", but later (more precisely) renamed the proton. He is also credited with developing the atomic numbering system alongside Henry Moseley. His other achievements include advancing the fields of radio communications and ultrasound technology.

Medical ultrasound includes diagnostic techniques (mainly imaging) using ultrasound, as well as therapeutic applications of ultrasound. In diagnosis, it is used to create an image of internal body structures such as tendons, muscles, joints, blood vessels, and internal organs, to measure some characteristics (e.g., distances and velocities) or to generate an informative audible sound. The usage of ultrasound to produce visual images for medicine is called medical ultrasonography or simply sonography. Sonography using ultrasound reflection is called echography. There are also transmission methods, such as ultrasound transmission tomography. The practice of examining pregnant women using ultrasound is called obstetric ultrasonography, and was an early development of clinical ultrasonography. The machine used is called an ultrasound machine, a sonograph or an echograph. The visual image formed using this technique is called an ultrasonogram, a sonogram or an echogram.

Ultrasound is composed of sound waves with frequencies greater than 20,000 Hz, which is the approximate upper threshold of human hearing. Ultrasonic images, also known as sonograms, are created by sending pulses of ultrasound into tissue using a probe. The ultrasound pulses echo off tissues with different reflection properties and are returned to the probe which records and displays them as an image.

Pulmonary edema (British English: oedema), also known as pulmonary congestion, is excessive fluid accumulation in the tissue or air spaces (usually alveoli) of the lungs. This leads to impaired gas exchange, most often leading to shortness of breath (dyspnea) which can progress to hypoxemia and respiratory failure. Pulmonary edema has multiple causes and is traditionally classified as cardiogenic (caused by the heart) or noncardiogenic (all other types not caused by the heart).

Various laboratory tests (CBC, troponin, BNP, etc.) and imaging studies (chest x-ray, CT scan, ultrasound) are often used to diagnose and classify the cause of pulmonary edema.

In physics, sound energy is a form of energy that can be heard by living things. Only those waves that have a frequency of 20 Hz to 20 kHz are audible to humans. However, this range is an average and will slightly change from individual to individual. Sound waves that have frequencies below 20 Hz are called infrasonic and those above 20 kHz are called ultrasonic. Sound is a longitudinal mechanical wave and as such consists physically in oscillatory elastic compression and in oscillatory displacement of a fluid. Therefore, the medium acts as storage for both potential and kinetic energy.

Consequently, the sound energy in a volume of interest is defined as the sum of the potential and kinetic energy densities integrated over that volume:

Ectopic pregnancy is a complication of pregnancy in which the embryo attaches outside the uterus. This complication has also been referred to as an extrauterine pregnancy (a.k.a. EUP). Signs and symptoms classically include abdominal pain and vaginal bleeding, but fewer than 50 percent of affected women have both of these symptoms. The pain may be described as sharp, dull, or crampy. Pain may also spread to the shoulder if bleeding into the abdomen has occurred. Severe bleeding may result in a fast heart rate, fainting, or shock. With very rare exceptions, the fetus is unable to survive.

Overall, ectopic pregnancies annually affect less than 2% of pregnancies worldwide. Risk factors for ectopic pregnancy include pelvic inflammatory disease, often due to chlamydia infection; tobacco smoking; endometriosis; prior tubal surgery; a history of infertility; and the use of assisted reproductive technology. Those who have previously had an ectopic pregnancy are at much higher risk of having another one. Most ectopic pregnancies (90%) occur in the fallopian tube, which are known as tubal pregnancies, but implantation can also occur on the cervix, ovaries, caesarean scar, or within the abdomen. Detection of ectopic pregnancy is typically by blood tests for human chorionic gonadotropin (hCG) and ultrasound. This may require testing on more than one occasion. Other causes of similar symptoms include: miscarriage, ovarian torsion, and acute appendicitis.

Congenital syphilis is syphilis that occurs when a mother with untreated syphilis passes the infection to her baby during pregnancy or at birth. It may present in the fetus, infant, or later. Clinical features vary and differ between early onset, that is presentation before 2-years of age, and late onset, presentation after age 2-years. Infection in the unborn baby may present as poor growth, non-immune hydrops leading to premature birth or loss of the baby, or no signs. Affected newborns mostly initially have no clinical signs. They may be small and irritable. Characteristic features include a rash, fever, large liver and spleen, a runny and congested nose, and inflammation around bone or cartilage. There may be jaundice, large glands, pneumonia (pneumonia alba), meningitis, warty bumps on genitals, deafness or blindness. Untreated babies that survive the early phase may develop skeletal deformities including deformity of the nose, lower legs, forehead, collar bone, jaw, and cheek bone. There may be a perforated or high arched palate, and recurrent joint disease. Other late signs include linear perioral tears, intellectual disability, hydrocephalus, and juvenile general paresis. Seizures and cranial nerve palsies may first occur in both early and late phases. Eighth nerve palsy, interstitial keratitis and small notched teeth may appear individually or together; known as Hutchinson's triad.

It is caused by the bacterium Treponema pallidum subspecies pallidum when it infects the baby after crossing the placenta or from contact with a syphilitic sore at birth. It is not transmitted during breastfeeding unless there is an open sore on the mother's breast. The unborn baby can become infected at any time during the pregnancy. Most cases occur due to inadequate antenatal screening and treatment during pregnancy. The baby is highly infectious if the rash and snuffles are present. The disease may be suspected from tests on the mother; blood tests and ultrasound. Tests on the baby may include blood tests, CSF analysis and medical imaging. Findings may reveal anemia and low platelets. Other findings may include low sugars, proteinuria and hypopituitarism. The placenta may appear large and pale. Other investigations include testing for HIV.