Stipa

Stipa is a genus of around 300 large perennial hermaphroditic grasses collectively known as feather grass, needle grass, and spear grass. They are placed in the subfamily Pooideae and the tribe Stipeae.

Many species are important forage crops. Several species such as Stipa brachytricha, S. arundinacea, S. splendens, S. calamagrostis, S. gigantea and S. pulchra are used as ornamental plants. One species, esparto grass (Stipa tenacissima), is used for crafts and extensively in paper making.

Ecology

Species of the genus Stipa can occur in grasslands or in savanna habitats. Certain specific prairie plant associations are dominated by grasses of the genus Stipa, which genus often lends its name to the terminology of some prairie types. In some areas of the western USA grasses of the genus Stipa form a significant part of the understory of Blue Oak savannas, and were even a more important element prehistorically before the invasion of many European grasses.

Selected species

Speech transmission index

Speech Transmission Index (STI) is a measure of speech transmission quality. The absolute measurement of speech intelligibility is a complex science. The STI measures some physical characteristics of a transmission channel (a room, electro-acoustic equipment, telephone line, etc.), and expresses the ability of the channel to carry across the characteristics of a speech signal. STI is a well-established objective measurement predictor of how the characteristics of the transmission channel affects speech intelligibility.

The influence that a transmission channel has on speech intelligibility is dependent on:

History

The STI was introduced by Tammo Houtgast and Herman Steeneken in 1971, and was accepted by Acoustical Society of America in 1980. Steeneken and Houtgast decided to develop the Speech Transmission Index because they were tasked to carry out a very lengthy series of dull speech intelligibility measurements for the Netherlands Armed Forces. Instead, they spent the time developing a much quicker objective method (which was actually the predecessor to the STI).