UHJ, BHJ, & B-FORMAT EXPLAINED

Ambisonics consists of the B-format and UHJ (BHJ) encoding.

B-FORMAT FOR MICROPHONES

B-format is used for multidirectional mics in 3 dimensions:

• W is an omnidirectional mic that gets all sounds from all directions at equal levels and phase.
• X is a figure-8 pattern with the + side pointing forward.
• Y is a figure-8 pattern with the + side pointing straight left.
• Z is a figure-8 pattern with the + side pointing straight up.

θ is the horizontal angle with front being 0 and clockwise rotation being positive.
ø is the vertical angle with the horizontal plane being 0 and up being positive.

• W = .707 mic
• X = mic cosθ cosø
• Y = mic sinθ cosø
• Z = mic sinø

This provides a method to record sounds from any 3-dimensional direction.

ENCODING B-FORMAT INTO UHJ DISTRIBUTION MEDIA

• S = .940W + .186X
• D = −.342Wj − .510Xj + .655Y
• L = .5S + .5D
• R = .5S − .5D
• L = .470W − .171Wj + .093X − .255Xj + .328Y
• R = .470W + .171Wj + .093X + .255Xj − .328Y
• T = −.143Wj + .651Xj − .707Y
• Q = 0.977Z

2 CHANNEL DISTRIBUTION MEDIA - BHJ

• L = .470W − .171Wj + .093X − .255Xj + .328Y
• R = .470W + .171Wj + .093X + .255Xj − .328Y

This is the only version commercially available.

The encoded material may be played in stereo or mono with no cancellation of back signals.

2.5 CHANNEL DISTRIBUTION MEDIA - SHJ

• L = .470W − .171Wj + .093X − .255Xj + .328Y
• R = .470W + .171Wj + .093X + .255Xj − .328Y
• T = −.143Wj + .651Xj − .707Y (limited bandwidth)

3 CHANNEL DISTRIBUTION MEDIA - THJ

• L = .470W − .171Wj + .093X − .255Xj + .328Y
• R = .470W + .171Wj + .093X + .255Xj − .328Y
• T = −.143Wj + .651Xj − .707Y

4 CHANNEL DISTRIBUTION MEDIA - PHJ

• L = .470W − .171Wj + .093X − .255Xj + .328Y
• R = .470W + .171Wj + .093X + .255Xj − .328Y
• T = −.143Wj + .651Xj − .707Y
• Q = .977Z

ENCODING UHJ DISTRIBUTION MEDIA FROM DOLBY SURROUND SPEAKER POSITIONS

• L = .83l + .12r + .56f + .38b + .09fj - .43bj
• R = .12l + .83r + .56f + .38b - .09fj + .43bj

DECODING UHJ DISTRIBUTION MEDIA BACK TO B-FORMAT

2.5, 3, and 4 channel media

• S = .5L + .5R
• D = .5L − .5R
• W = .982S + .163Dj + .151Tj
• X = .419S − .828Dj + .768Tj
• Y = .796D − .676T + .187Sj
• Z = 1.023Q (only 4 channel media)

2 channel media

• S = .5L + .5R
• D = .5L − .5R
• W = .982S + .164Dj
• X = .419S − .828Dj
• Y = .796D + .385Sj

DECODING QUADRAPHONIC FROM B-FORMAT

• lf = 4W + 2.83X + 2.83Y
• rf = 4W + 2.83X − 2.83Y
• lb = 4W − 2.83X + 2.83Y
• lf = 4W − 2.83X − 2.83Y

DECODING DISTRIBUTION MEDIA TO DOLBY SURROUND SPEAKERS

• l = .83L + .12R
• r = .12L + .83R
• f = .56L + .09Lj + .56R - .09Rj
• b = .38L - .43Lj + .38R + .43Rj