dB laws, etc.

• speed of sound is 1130 ft/sec, 345 m/s
• 0 dB SPL = 0.0002 ubar (this is the lowest level 1 kHz tone the average person can detect)
• 1W of acoustic power = 112 dB SPL 1m
• density of air = Ro = 1.18 kg/m^3
• 1 atm = 101.325 kPa = 14.7 psi
• 1 Pa = 1 N / m^2
• sealed, second order alignment = -12dB/octave roll off slope
• vented, fourth order alignment = -24dB/octave roll off slope
• a 10dB increase in SPL = an apparent doubling of loudness
• ISO standard 1/3 octave frequency bands
  • 20Hz 25 30.5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1k 1.25 1.6k 2k 2.5k 3.15k 4k 5k 6.3k 8k 10k 12.5k 16k 20kHz
• video bandwidth
  • Standard TV NTSC: 525 (lines) X 30 Hz (refresh) = 15.75 kHz
  • Line doubler: 1050 (lines) X 30 Hz (refresh) = 31.5 kHz
  • Line quadrupler: 2100 (lines) X 30 Hz (refresh) = 63 kHz
• CCIR601
  • NTSC 720 (H) x 478 (V) max, 60 fields/sec interlaced, 30 frames/sec
  • PAL 720 (H) x 573 (V) max, 50 fields/sec interlaced, 25 frames/sec
  • 720x480 NTSC, 720x576 PAL are also commonly referred to
• lines of resolution (horizontal)

  source	lines
  VHS	220
  broadcast	330
  laserdisc	425
  DVD	480
  CCIR601	480

  
  
• P = E^2 / Z which is watts = volts^2 / impedence
• V = IR which is volts = current * resistance
• The Sony DVP-S7000 secret service mode:
  • OFF, be in stand by mode
  • then sequentially hit TIME CLEAR POWER
• units conversion
  • 1 m = 39.37 inches, 1 inch = 2.54 cm
  • 1 kg = 2.205 lb
  • 28.317 L = 1 cu ft
• logarithmic rules
  • y = logb x : x = b^y
  • log PQ = log P + log Q
  • log P/Q = log P - log Q
  • logb P^n = n logb P
  • b^logb(P) = P
• Some excursion limited formula
  • Xmax limited SPL = 112 + 10 log(4 pi Ro/c Vd^2 f^4)
  • Xpeak = (r=1m) (20uN/m^2) 10^SPL/20 / (Ro pi^2 f^2 a^2)
  • Xpeak = (1.18 x 10^3) * 10^SPL/20 / (f^2 * a^2)
• sine wave amplitude relationships (voltage, current, SPL)
  • RMS = peak / sqrt(2) = 0.707 peak
  • RMS = pi * average / (2 * sqrt(2)) = 1.1 average
  • peak = sqrt(2) * RMS = 1.414 RMS
  • peak = (pi / 2) * average = 1.57 average
• max DVD bitrate = 10.08 Mbps
  
  
• Discrete digital audio formats

  	CD/LD linear PCM	AC3	DTS	MPEG2 audio	SDDS	future PCM?
  sampling frequency	44.1kHz	48kHz	48kHz	48kHz	48kHz	48 / 96kHz
  bits per sample	16 bits	compressed	compressed	compressed	compressed	16 / 20 / 24 bits
  bit rate	1411kbps	640kbps max	1536kbps	1280kbps max	912kbps max	6144kbps
  number of channels	2	5.1 max	5.1 max	7.1 max	7.1 max	8 max

  
  
• A & C weighted frequency response

  Hz	A (dB)	C (dB)
  10	-70.4	-14.3
  12.5	-63.4	-11.2
  16	-56.7	-8.5
  20	-50.5	-6.2
  25	-44.7	-4.4
  31.5	-39.4	-3.0
  40	-34.6	-2.0
  50	-30.2	-1.3
  63	-26.2	-0.8
  80	-22.5	-0.5
  100	-19.1	-0.3
  125	-16.1	-0.2
  160	-13.4	-0.1
  200	-10.9	0.0
  250	-8.6	0.0
  315	-6.6	0.0
  400	-4.8	0.0
  500	-3.2	0.0
  630	-1.9	0.0
  800	-0.8	0.0
  1000	0.0	0.0
  1250	+0.6	0.0
  1600	+1.0	-0.1
  2000	+1.2	-0.2
  2500	+1.3	-0.3
  3150	+1.2	-0.5
  4000	+1.0	-0.8
  5000	+0.5	-1.3
  6300	-0.1	-2.0
  8000	-1.1	-3.0
  10000	-2.5	-4.4
  12500	-4.3	-6.2
  16000	-6.6	-8.5
  20000	-9.3	-11.2

  
  
• The chromatic scale with A4=440Hz

  note	octave	Hz
  C	-3	2.0439
  C#	-3	2.1655
  D	-3	2.2943
  Eb	-3	2.4307
  E	-3	2.5752
  F	-3	2.7283
  F#	-3	2.8906
  G	-3	3.0625
  G#	-3	3.2446
  A	-3	3.4375
  Bb	-3	3.6419
  B	-3	3.8585
  C	-2	4.0879
  C#	-2	4.3310
  D	-2	4.5885
  Eb	-2	4.8614
  E	-2	5.1504
  F	-2	5.4567
  F#	-2	5.7812
  G	-2	6.1249
  G#	-2	6.4891
  A	-2	6.8750
  Bb	-2	7.2838
  B	-2	7.7169
  C	-1	8.1758
  C#	-1	8.6620
  D	-1	9.1770
  Eb	-1	9.7227
  E	-1	10.3009
  F	-1	10.9134
  F#	-1	11.5623
  G	-1	12.2499
  G#	-1	12.9783
  A	-1	13.7500
  Bb	-1	14.5676
  B	-1	15.4339
  C	0	16.3516
  C#	0	17.3239
  D	0	18.3540
  Eb	0	19.4454
  E	0	20.6017
  F	0	21.8268
  F#	0	23.1247
  G	0	24.4997
  G#	0	25.9565
  A	0	27.5000
  Bb	0	29.1352
  B	0	30.8677
  C	1	32.7032
  C#	1	34.6478
  D	1	36.7081
  Eb	1	38.8909
  E	1	41.2034
  F	1	43.6535
  F#	1	46.2493
  G	1	48.9994
  G#	1	51.9131
  A	1	55.0000
  Bb	1	58.2705
  B	1	61.7354
  C	2	65.4064
  C#	2	69.2957
  D	2	73.4162
  Eb	2	77.7817
  E	2	82.4069
  F	2	87.3071
  F#	2	92.4986
  G	2	97.9989
  G#	2	103.8262
  A	2	110.0000
  Bb	2	116.5409
  B	2	123.4708
  C	3	130.8128
  C#	3	138.5913
  D	3	146.8324
  Eb	3	155.5635
  E	3	164.8138
  F	3	174.6141
  F#	3	184.9972
  G	3	195.9977
  G#	3	207.6523
  A	3	220.0000
  Bb	3	233.0819
  B	3	246.9417
  C	4	261.6256
  C#	4	277.1826
  D	4	293.6648
  Eb	4	311.1270
  E	4	329.6276
  F	4	349.2282
  F#	4	369.9944
  G	4	391.9954
  G#	4	415.3047
  A	4	440.0000
  Bb	4	466.1638
  B	4	493.8833
  C	5	523.2511
  C#	5	554.3653
  D	5	587.3295
  Eb	5	622.2540
  E	5	659.2551
  F	5	698.4565
  F#	5	739.9888
  G	5	783.9909
  G#	5	830.6094
  A	5	880.0000
  Bb	5	932.3275
  B	5	987.7666
  C	6	1046.5023
  C#	6	1108.7305
  D	6	1174.6591
  Eb	6	1244.5079
  E	6	1318.5102
  F	6	1396.9129
  F#	6	1479.9777
  G	6	1567.9817
  G#	6	1661.2188
  A	6	1760.0000
  Bb	6	1864.6550
  B	6	1975.5332
  C	7	2093.0045
  C#	7	2217.4610
  D	7	2349.3181
  Eb	7	2489.0159
  E	7	2637.0205
  F	7	2793.8259
  F#	7	2959.9554
  G	7	3135.9635
  G#	7	3322.4376
  A	7	3520.0000
  Bb	7	3729.3101
  B	7	3951.0664
  C	8	4186.0090
  C#	8	4434.9221
  D	8	4698.6363
  Eb	8	4978.0317
  E	8	5274.0409
  F	8	5587.6517
  F#	8	5919.9108
  G	8	6271.9270
  G#	8	6644.8752
  A	8	7040.0000
  Bb	8	7458.6202
  B	8	7902.1328
  C	9	8372.0181
  C#	9	8869.8442
  D	9	9397.2726
  Eb	9	9956.0635
  E	9	10548.0818
  F	9	11175.3034
  F#	9	11839.8215
  G	9	12543.8540
  G#	9	13289.7503
  A	9	14080.0000
  Bb	9	14917.2404
  B	9	15804.2656
  C	10	16744.0362
  C#	10	17739.6884
  D	10	18794.5451
  Eb	10	19912.1270
  E	10	21096.1636
  F	10	22350.6068
  F#	10	23679.6431
  G	10	25087.7079
  G#	10	26579.5006
  A	10	28160.0000
  Bb	10	29834.4807
  B	10	31608.5313