Resonance

In physics, resonance is a phenomenon that occurs when a vibrating system or external force drives another system to oscillate with greater amplitude at a specific preferential frequency.

Frequencies at which the response amplitude is a relative maximum are known as the system's resonant frequencies, or resonance frequencies. At resonant frequencies, small periodic driving forces have the ability to produce large amplitude oscillations. This is because the system stores vibrational energy.

Resonance occurs when a system is able to store and easily transfer energy between two or more different storage modes (such as kinetic energy and potential energy in the case of a pendulum). However, there are some losses from cycle to cycle, called damping. When damping is small, the resonant frequency is approximately equal to the natural frequency of the system, which is a frequency of unforced vibrations. Some systems have multiple, distinct, resonant frequencies.

Resonance phenomena occur with all types of vibrations or waves: there is mechanical resonance, acoustic resonance, electromagnetic resonance, nuclear magnetic resonance (NMR), electron spin resonance (ESR) and resonance of quantum wave functions. Resonant systems can be used to generate vibrations of a specific frequency (e.g., musical instruments), or pick out specific frequencies from a complex vibration containing many frequencies (e.g., filters).

Sonorant

In phonetics and phonology, a sonorant or resonant is a speech sound that is produced with continuous, non-turbulent airflow in the vocal tract; these are the manners of articulation that are most often voiced in the world's languages. Vowels are sonorants, as are consonants like /m/ and /l/: approximants, nasals, flaps or taps, and most trills.

In older usage, only the term resonant was used with this meaning, and sonorant was a narrower term, referring to all resonants except vowels and semivowels.

Types

Whereas obstruents are frequently voiceless, sonorants are almost always voiced. A typical sonorant consonant inventory found in many languages comprises the following: two nasals /m/, /n/, two semivowels /w/, /j/, and two liquids /l/, /r/.

In the sonority hierarchy, all sounds higher than fricatives are sonorants. They can therefore form the nucleus of a syllable in languages that place that distinction at that level of sonority; see Syllable for details.

Sonorants contrast with obstruents, which do stop or cause turbulence in the airflow. The latter group includes fricatives and stops (for example, /s/ and /t/).