Meter is the regular perceived grouping of beats in a rhythm. Perceptions of meter create metrical accents, which are implied accents based on the form of the measure (duple, triple etc). Metrical accents can be brought out by phenomenal or structural accents or may merely be perceived due to a regular grouping of notes.
Time signature specifies the divisions of the meter, but meter exists absent from an explicitly stated time signature, which is useful mostly for purposes of notation. On the contrary, work by Desain and Honing (1989) indicates that meter can be derived from levels of grouping in rhythm, meaning that it in fact may correspond to an actual emergent phenomenon, rather than a perceived or notated phenomenon (Clarke 491).
Richard Parncutt explains that the salience of a perceived meter may be estimated by adding together the saliences of consonant pulse sensations.
Lerdahl and Jackendoff describe meter as something that arises from patterns of accent and define metrical structure as “the regular, hierarchical pattern of beats to which the listener relates musical events” (17). As Lerdahl and Jackendoff write, “the listener’s cognitive task is to match the given pattern of phenomenal accentuation as closely as possible to a permissible pattern of metrical accentuation; where the two patterns diverge, the result is syncopation, ambiguity, or some other kind of rhythmic complexity” (Lerdahl and Jackendoff 1983, 18). Additionally, Lerdahl and Jackendoff stipulate that beats must be evenly spaced, that listeners tend to perceive meters that are not too far from the tactus, and that metrical structure is a relatively local phenomenon, in contrast with grouping, which exists at all levels of a piece.