why do the tabla drums have a black spot in the middle of the drum head
Tabla The head of each drum has a central area of "tuning paste" called the syahi (lit. "ink"; a.k.a. shāī or gāb). This is constructed using multiple layers of a paste made from starch (rice or wheat) mixed with a black powder of various origins. The precise construction and shaping of this area is responsible for modification of the drum's natural overtones, resulting in the clarity of pitch (see inharmonicity) and variety of tonal possibilities unique to this instrument which has a bell-like sound. The skill required for the proper construction of this area is highly refined and is the main differentiating factor in the quality of a particular instrument.
Stereocilia (inner ear) As acoustic sensors in mammals, stereocilia are lined up in the organ of Corti within the cochlea of the inner ear. In hearing, stereocilia transform the mechanical energy of sound waves into electrical signals for the hair cells, which ultimately leads to an excitation of the auditory nerve. Stereocilia are composed of cytoplasm with embedded bundles of cross-linked actin filaments. The actin filaments anchor to the terminal web and the top of the cell membrane and are arranged in grade of height.[2] As sound waves propagate in the cochlea, the movement of endolymph fluid bends the stereocilia. If the direction of movement is towards the taller stereocilia, tension develops in the tip links, mechanically opening transduction channels near the tips. Cations from the endolymph flow into the cell, depolarizing the hair cell and triggering the release of neurotransmitters to nearby nerves, which send an electrical signal to the central nervous system.