My mind erases

Retention period: As long as needed or wanted.

Surfing through some old papers, I found this. And looking at it, I have no idea what it is at first glance.

Nothing really to talk about other than I feel like shit, but here it is...I think some smarter people may know what this used to help me with.

-Longitudnal waves deal with wiggling the air molecules back and forth in the direction of the wave.
-Transverse waves acts like the motion of a rope shaken up and down at one end. (perpendicular)
-Slope of a graph of position vs. time is equal to velocity.
-Newton’s 2nd law: F=MA
-Acceleration is the change in velocity over the change in time.
-Pressure is the application of force acting perpendicular to surface area.
-Force deals wither either a push or pull, may distort the object, changes it’s motion.
-Pressure is a force distributed over a certain area. P = F / A
-Work is done when a force is applied to an object that moves = F(D)
-Pressure of the atmosphere on our bodies is 10^5 Newtons / Meters^2 (15lbs/in^2) at sea
-Formula for a displaced guitar string: Potential energy = (2T / L)y^2 where T is equal to the tension in the string, L = length of string and Y is the distance of displacement
-Speed of sound: 343 m/s Gravity: 9.8 m/s^2 .305 meters in 1 ft
1 kg = 2.2 lbs 1 pascal = 1 N/m^2
-Difference between light and sound? About 10^6 m/s
-Kinetic energy = 1/2 M V^2 where M = mass and V = velocity
-Potential energy of a raised object = MGH where M = mass, G = gravity, H = Height
-Equation for a spring: F = -K(y) where Force (F) acts on K (spring constant) with
displacement of (y).
-Frequency of vibration is caculated: f = 1/T where T is the period of one vibration
-Frequency in hertz: f = 1 / 2(pie) * sqroot: (K / M)-Frequency of a pendulum: f = ½(pie) * sqroot (g / l) where g = gravity, and l = lenth
-Frequency of helmholtz resonator: f = [V / 2(pie)]* sqroot (a / VL) a is neck. V is
volume and L is the length of the neck.
-Tuning forks, principal mode will be struck at the bottom, clang mode near the top. Best
position to listen to a tuning fork is between the prongs at the top.
-Node: an area where there is no vibration, where sinusoidal graph intersects 0.
-One cent = 1/100th of a half-step
-Log functions are typically Logbase10, (Logbase10)100 = 2.
-(Log base 10)1 = 0 because 10^0 = 1, (logbase10)10 = 1 because 10^1 = 10
-If (log base 10)2 = .3, then we can derive (logbase10)4 by saying 2(log10)2 = .6
(logbase10)6 by saying 3(log10)2 = .9
-Frequency ratios: in logbase2, equation: 1200 X logbase2 (F2 / F1)
-Given 386.3cent, what is the frequency ratio?
386.3 = 1200(logbase2)(F2/F1)
386.3/1200 = logbase2(F2/F1)
2^(386.3/1200) = F2/F1 >>> 1.25 or 5/4
-Decibels: in logbase10, equation: 10logbase10
-Wave velocity equation: V = f(lambda) where f = frequency and lam = wavelength.
If “f” waves pass and crest at lambda meters apart^^^
-Longitudinal waves travel at v = sqroot (E / P) where E = elasticity, and P is density.
-Reflection of sound: The angle of incidence is equal to angle of reflection. The
reflected transverse wave is reflected like in a mirror when returning.

-Frequencies increase as you go towards the source (higher tone), lower when moving
away from the source.
-Speed of sound waves in ideal gas formula: V = sqroot: (Y R T / M) where Y and R are
constants for the gas, T is absolute temperature and M is molecular weight of gas.
-Doppler effect frequency: F = [Fs](V+Vo/V) where Fs is frequency of the source, Vo
is the speed of the observer, and V is speed of sound.
-If the source is in motion then the equation is F = [Fs](V/V-Vs) where Vs is
the speed of the source.
-Refraction occurs when the speed of waves changes which can result in a change in
direction or propagation.
-Diffraction occurs when waves encounter an obstacle, they bend around the obstacle.
-Frequency of modes equation to the nth mode: Fn = n(v/2L) where L is the length
of a string with both ends fixed, and N is the number mode currently in.
-In a bar or rod: fn = n/2L * sqroot: (E/p) where E is young’s elastic modulous and for
the material, p is it’s density.
-For a vibrating string: Fn = (n/2L) * sqroot: (T/u) where T = tension in the
string and u is equal to the mass per unit of length.
-Find first 2 modes of vibration of pipe .75 m long:
f1 = v/2L = 343 / 2(.75) = 229 Hz
f2 = 2v/2L = 2(343) / 2(.75) = 457 Hz
-Acoustic Impedance equation: Za = p / U where p = sound pressure to volume velocity
U. Measured in acoustic Ohms.