Musical instruments that start with the letter I include the igil, ipu, Irish uillean, Irish bouzouki, ichigenkin, inci, iya, itotele and istarski mih. The instruments originate from countries ranging from Cuba and Ireland to Croatia, Japan and the Philippines.
Bessel's functions are often used in acoustics for describing circular membranes behaviour (exploited by most of the musical instruments). They are the solutions of the wave equations using polar coordinates. Set the properties of the membrane Bessel's functions describe the vibrational modes of the membrane.
Mussels play an important role in the aquatic ecosystem. Many different kinds of wildlife eat mussels, including raccoon, otters, herons, and egrets. Mussels filter water for food and thus are a purification system. They are usually present in groups called beds.