Resonance Small periodic oscillations produce large amplitude oscillations

Resonance • Small periodic oscillations produce large amplitude oscillations • Swing example – add E at just the right time = larger amplitude oscillations

Acoustic resonance • The tendency of an acoustic system to absorb more energy when it is driven at a frequency that matches one of its own natural frequencies of vibration. • http: //www. youtube. com/watch? v=17 tq. Xgv. CN 0 E • Acoustics is the study of mechanical waves in solids, liquids, and gases.

Closed end tubes • Wind instruments have resonant frequencies that correspond to the length of the tube. • The fundamental frequency is the most basic wave form that will produce a resonant frequency in the tube (the fundamental frequency of the slinky) • Qualifier: the antinode will be present at the open end and the node at the closed end

• An acoustically resonant object usually has more than one resonance frequency, especially at harmonics of the strongest resonance. • Recall that harmonics refers to the harmonious sounds produced by wave interactions (interference patterns) of waves that have lengths that are whole number ratios. • An octave is a 2: 1 ratio, a fifth is a 3: 2 ratio • Demonstration with resonance tubes • www. youtube. com/watch? v=K_T-w 3 D 2 QKY

Resonance on a large scale Tesla story the first few minutes https: //www. youtube. com/watch? v=l 5 r. EW 9 Qg. JDc

Wave interference and Beat Frequency And you

Wave interference

Demonstration with beat boxes • Creation of a beat frequency

BEATS • Periodic and repeating fluctuations heard in the intensity of a sound when two sound waves of similar frequencies interfere with each other. • https: //www. youtube. com/watch? v=p. Rp. N 9 u. Liou. I

• The beat frequency = the difference in the frequency of the two notes. • Ex: 2 sound waves with 256 and 254 Hz are played at the same time, a beat frequency of 2 Hz will be detected.

Multiple frequency interference (music when a mathematical relationship is present)

Binaural beats • https: //www. youtube. com/watch? v=zv. TYxjp. P 6 H 4 • https: //www. youtube. com/watch? v=0 k. QKr. TOCOt. Q • https: //www. youtube. com/watch? v=a. Xi_h. Id 0 vp. U

Wave interference in the room with tone generator • http: //www. szynalski. com/tone-generator/

Acoustics • https: //www. youtube. com/watch? v=JPYt 10 zrcl. Q • https: //www. youtube. com/watch? v=m. XVGIb 3 bz. HI • GO TO auditorium to see acoustic panels

Wave interference patterns Destructive interference = 1 peak 1 + trough 2 = cancel out = 0 amplitude = no sound 2 Constructive interference = peak 1 + peak 2 = double amplitude double the sound (also with trough and trough)

p. HET simulation with questions