Small birds like Sparrows, Parakeets and especially Carolina Wren can chirp so loud that this could be sometimes irritating for the close listener instead of pleasing. A person might wonder how it is possible that a small living being can sound so much louder.
Actually, sounds produced by small birds have high pitch and also high frequency. A very high pitched sound can be teasing for human ears if a person is very close to the source. The idea has been taken and therefore, sirens and fire alarms are designed to produce high pitched sharp noise. This is necessary to alert people. Sharp sounds can also be heard from far distance.
Birds do not have vocal cords like mammals. Syrinx, the vocal organ of birds is responsible for sounds produced by them. Syrinx word comes from Greek language which means pan pipes or pan flute. Pan flute is an ancient Greek musical instrument which works on the principle of closed tubes. Since vocal organ of a bird is somewhat similar to this musical instrument therefore, it has been given the name of syrinx.
Syrinx is extremely small in size. Its size varies with the size of a bird. Syrinx is located at the lower end of trachea (wind pipe). Despite of its small size, it can produce extremely loud chirping.
Regarding a question, why do birds chirp so loud in the morning? During early morning, since there is silence in the environment because people are still sleeping, their sounds appear to be more louder than what it is at noon or in the evening.