Resonance

WIND INSTRUMENTS

Clarinets, flute, saxophone, trumpet are examples of wind musical instruments. A musical note originates from a source vibrating in a uniform manner with one or more constant frequencies music is a combination of musical notes. All wind instrument use resonating

air columns to produce their sounds.  Sounds from wind instruments may originate from:

1. Air vibrating over an opening e.g. organ and flute
2. The vibrating lips of a brass instrument e.g. trumpet

• A vibrating heel e.g. clarinet, saxophone

Some columns are of fixed length, their resonant frequencies being altered by the opening or the closing of holes in the column e.g. clarinet, a recorder, some instruments are played by altering the length the air column e.g. trumpet.

STRINGED INSTRUMENTS

The guitar, the sonometer and piano are examples of stringed musical instruments. These instruments may be set in vibration by a bow, or plucked with a finger e.g. a violin is bowed while a guitar is plucked. The frequency of a vibrating string depends on its length, the mass and the force that keeps the string taut. Stringed instruments vibrate as a whole and in loops at the same time e.g. the violin. These vibrations produce both the fundamental and overtones frequencies.

PERCUSSION INSTRUMENTS (drums, bell, talking drum)

Percussion instruments produce musical notes when they are struck or hit. They have rods, plates or membranes that vibrate when struck; for example, there are rods in bells, plates (bars) in xylophones and membrane in drums.

ECHOES AND THEIR APPLICATION

An echo is the repetition of sounds caused by the reflection of sound waves from a hard surface. Buildings, walls and cliffs are good reflector of sound.

CLASSWORK 9

Write short note on the following with two examples each

1. Percussion instruments
2. Wind instruments
3. Stringed instruments

ASSIGNMENT 9

SECTION A

1. In stringed instruments like a guitar or violin, high pitched notes are produced by strings that are (a) thick and short (b) thin and short (c) thick and long (d) thin and long
2. When the length of a vibrating string is tripled, its frequency of vibration (a) becomes three times the former value (b) becomes one-third its former value (c) becomes six times its former value (d) becomes one-sixth the former value
3. A tuning fork sounds louder when its stem is pressed against a table top than when held in air because (a) a larger mass of air is set vibrating by the table top (b) the whole table vibrates in resonance (c) the whole table has acquire a larger frequency (d) the fork and the table have the same frequency
4. What type of motion does the skin of a talking drum perform when it is being struck with drumstick? (a) random (b) rotational (c) vibratory (d) translational
5. Calculate the wavelength of a note which is one octave lower than a note of 256 Hz in a medium in which the speed of sound is 352m/s (a) 0.69m (b) 1.38m (c) 2.75m (d) 5.50m

SECTION B

Distinguish between noise and musical note

What is echo? Why is considered a nuisance?

Explain the terms; fundamental note, overtones harmonics and intensity