tmmi.m

function Zin = tmmi( boreData, holeData, endType, f, lossType, T )
% TMMI: Compute the normalized input impedance of a system using the
%       transfer matrix method with external tonehole interactions.
%
% ZIN = TMMI( BOREDATA, HOLEDATA, ENDTYPE, F, LOSSTYPE, T ) returns the
% input impedance of a system defined by BOREDATA and HOLEDATA, normalized
% by the characteristic impedance at the input, at frequencies specified in
% the 1D vector F, given an optional air temperature T in degrees Celsius
% (default = 20 C). The parameter ENDTYPE specifies the bore end condition
% [0 = rigidly closed; 1 = unflanged open; 2 = flanged open; 3 = ideally
% open (Zl = 0)]. The optional parameter LOSSTYPE specifies how losses are
% approximated [0 = no losses; 1 = lowest order losses (previous tmm
% method, default); 2 = Zwikker-Kosten; 3 = full Bessel function
% computations].
%
% BOREDATA is a 2D matrix, with values in the first row corresponding to
% positions along the center axis of a specified geometry, from input to
% output ends, and values in the second row corresponding to radii at those
% positions (all values in meters).
%
% HOLEDATA is a 2D matrix specifying information about holes along a
% geometry. HOLEDATA can be empty ([]) or given by zeros(6, 0) if no holes
% exist. If holes do exist, the first row specifies positions along the
% center axis and each subsequent row specifies corresponding hole radii,
% hole heights, hole protrusion lengths, hole states (open or closed), pad
% states, pad radii, pad heights and wall thicknesses (all values, other
% than states, are in meters).
%
% Initially by Gary P. Scavone, McGill University, 2013-2024, updates
% provided by Champ Darabundit, 2023.
%
% References:
%
% 1. Lefebvre, A., Scavone, G. and Kergomard, J. (2013), "External Tonehole
%      Interactions in Woodwind Instruments." Acta Acustica united with
%      Acustica, vol. 99, pp. 975-985.
%
% 2. Kergomard, J. (1989), "Tone hole external interactions in woodwind
%      musical instruments." Proceedings of the 1989 Congress on Acoustics,
%      Belgrade.

if nargin < 4 || nargin > 6
  error( 'Invalid number of arguments.');
end
if ~isvector(f)
  error( 'f should be a 1D vector of frequencies in Hertz.' );
end
if ~exist( 'T', 'var')
  T = 20;
end
if ~exist( 'lossType', 'var')
  lossType = 1;
end
if isempty( holeData )
  holeData = zeros(6, 0);
end

% Calculate and use mutual radiation impedances. If this is false, the
% calculations should be equivalent to the TMM.
doInteractions = true;
  
% Bore dimensions
idx = find(diff(boreData(1,:)) == 0);
boreData(1, idx+1) = boreData(1, idx+1) + eps; % avoid double values
x = sort( [boreData(1,:) holeData(1,:)] ); % segment positions along x-axis
L = diff( x );                             % lengths of segments

isHole = zeros(size(x));                   % is x value at a tonehole?
for n = 1:length(x)
  isHole(n) = 1 - isempty(find(x(n)==holeData(1,:), 1));
end

% Interpolate bore radii at x values
ra = interp1(boreData(1,:), boreData(2,:), x, 'linear');

% Tonehole dimensions and states
rb = holeData(2,:).';            % tonehole radii
t = holeData(3,:).';             % tonehole heights
chimney = holeData(4,:);         % tonehole chimney height
states = holeData(5,:);          % tonehole states
[n, m] = size(holeData);
padr = zeros(1, m);
padt = zeros(1, m);
holew = zeros(1, m);
if n > 6, padr = holeData(7,:); end % tonehole pad radii
if n > 7, padt = holeData(8,:); end % tonehole pad heights
if n > 8, holew = holeData(9,:); end % tonehole wall thickness

if f(1) == 0 % avoid zero frequency calculations
  f(1) = eps;
end

nOth = sum( states );   % number of open toneholes

% Check pipe end condition
nOpen = nOth;
if endType
  nOpen = nOth + 1;
end

if nOpen < 2  % Do TMM
  Zin = tmm( boreData, holeData, endType, f, lossType, T );
  return
end

% Determine indices of open holes in position and tonehole vectors
oidx = find(states);           % open tonehole indices (relative to all toneholes)
xidx = find(isHole);           % x-indices of holes
xidx = [xidx(oidx) length(x)]; % x-indices of open tone holes + end
ds = holeData(1, oidx);        % positions of open holes
ras = ra(isHole>0);            % radii at all toneholes

% Allocate various matrices
Ymunm1 = 0;
Ypnm1 = 0;
ZB = zeros( nOpen, nOpen, length(f) );
Y = zeros( nOpen, nOpen, length(f) );

[c, rho] = thermoConstants( T );
k = 2 * pi * f / c;

for n = 1:nOth

  nHole = oidx(n);
  Gamma = sectionLosses( rb(nHole), rb(nHole), 0, f, T, lossType );
  [~, B, C, ~] = tmmTonehole( rb(nHole)/ras(nHole), rb(nHole), t(nHole), ...
    states(nHole), Gamma, '', T, chimney(nHole), padr(nHole), ...
    padt(nHole), holew(nHole) );
      
  % Diagonals of (Z+B) matrix are open hole shunt impedances.
  ZB(n, n, :) = 1 ./ C;
  
  % Compute other Z terms (mutual radiation impedances)
  if doInteractions
    for m = 1:nOth
      if m == n, continue; end
      dnm = abs( ds(n) - ds(m) );
      %ZB(n, m, :) = 1j*rho*c*k.*exp(-1j*k*dnm)/(4*pi*dnm);
      ZB(n, m, :) = 1j*rho*f.*exp(-1j*k*dnm)/(dnm); % extra factor of 2
    end
  end
    
  % Compute Y elements: Start with 1/2 of series length correction for
  % current open hole.
  MA = 1; MB = B/2; MC = 0; MD = 1;

  % Cascade all sections between current open hole and the next open hole.
  for m = xidx(n):xidx(n+1)-1
    if isHole(m)
      if states(nHole) == 0 % closed
        Gamma = sectionLosses( rb(nHole), rb(nHole), 0, f, T, lossType );
        [A, B, C, D] = tmmTonehole( rb(nHole)/ras(nHole), rb(nHole), ...
          t(nHole), states(nHole), Gamma, '', T, chimney(nHole), ...
          padr(nHole), padt(nHole), holew(nHole) );
        MAT = MA.*A + MB.*C;
        MBT = MA.*B + MB.*D;
        MCT = MC.*A + MD.*C;
        MDT = MC.*B + MD.*D;
        MA = MAT; MB = MBT; MC = MCT; MD = MDT;
      end
      nHole = nHole + 1;
    end
    
    % Cascade cylindrical or conical sections
    if L(m) < eps, continue; end % skip if at a diameter discontinuity
    [Gamma, Zc] = sectionLosses( ra(m), ra(m+1), L(m), f, T, lossType );
    [A, B, C, D] = tmmCylCone( ra(m), ra(m+1), L(m), Gamma, Zc );
    MAT = MA.*A + MB.*C;
    MBT = MA.*B + MB.*D;
    MCT = MC.*A + MD.*C;
    MDT = MC.*B + MD.*D;
    MA = MAT; MB = MBT; MC = MCT; MD = MDT;
  end

  % Finally, include 1/2 of series length correction of next open hole
  % (if not the end hole).
  if n < nOth
    nHole = oidx(n+1);
    Gamma = sectionLosses( rb(nHole), rb(nHole), 0, f, T, lossType );
    [~, B, ~, ~] = tmmTonehole( rb(nHole)/ras(nHole), rb(nHole), ...
      t(nHole), states(nHole), Gamma, '', T, chimney(nHole), ...
      padr(nHole), padt(nHole), holew(nHole) );
    B = B/2; C = 0; A = 1; D = 1;
    MAT = MA.*A + MB.*C;
    MBT = MA.*B + MB.*D;
    MCT = MC.*A + MD.*C;
    MDT = MC.*B + MD.*D;
    MA = MAT; MB = MBT; MC = MCT; MD = MDT;
  end

  % Fill Y matrix from cascaded terms.
  if n > 1
    Y(n,n-1,:) = Ymunm1;
  end
  Y(n,n,:) = Ypnm1 + MD./MB;
  if n < nOpen
    Y(n,n+1,:) = -1./MB;
    Ymunm1 = -1./MB;
    Ypnm1 = MA./MB;
  end

end

% Now handle end condition
if endType
  switch endType
    case 1
      ZB(nOpen,nOpen,:) = radiation( ra(end), f, T, 'dalmont'); % self-radiation
    case 2
      ZB(nOpen,nOpen,:) = radiation( ra(end), f, T, 'flanged'); % self-radiation
    case 3
      ZB(nOpen,nOpen,:) = zeros(size(k));
  end
  if doInteractions
    for m = 1:nOth
      dnm = abs( x(end) - ds(m) );
      ZB(nOpen, m, :) = 1j*rho*f.*exp(-1j*k*dnm)/(2*dnm);
    end
  end
  Y(nOpen,nOpen-1,:) = Ymunm1;
  Y(nOpen,nOpen,:) = Ypnm1;
else % end is closed
  Y(nOth,nOth,:) = Ypnm1 + MC./MA;
end

% Compute Eqs. 14 & 10 for each frequency
I = eye(nOpen);
U = zeros(nOpen, length(k));
P = zeros(nOpen, length(k));
Us = zeros(nOpen, 1);
Us(1) = 1;
for n = 1:length(k)
  U(:, n) = ( I + Y(:, :, n)*ZB(:, :, n) )^(-1) * Us;
  P(:, n) = ZB(:, :, n) * U(:, n);
end
  
% Compute "load" impedance of section rightward from first open hole
%Zl = (P(1, :) ./ U(1, :));
Zl = P(1, :);  % since Us(1) = 1

% If there is at least one open tonehole, account for 1/2 of its series
% impedance on the upstream side.
if ~isempty( oidx )
  nHole = oidx(1);
  Gamma = sectionLosses( rb(nHole), rb(nHole), 0, f, T, lossType );
  [~, B, ~, D,] = tmmTonehole( rb(nHole)/ras(nHole), rb(nHole), ...
    t(nHole), states(nHole), Gamma, '', T, chimney(nHole), ...
    padr(nHole), padt(nHole), holew(nHole) );
  Zl = (Zl + B) ./ D;
  nHole = nHole - 1; % decrement hole counter
else % no open holes
  nHole = sum(isHole);
end

% Continue back through the remainder of the closed system using the TMM
% (from the first closed hole upstream of most upstream open hole).
for n = xidx(1)-1:-1:1
  if L(n) > eps
    [Gamma, Zc] = sectionLosses( ra(n), ra(n+1), L(n), f, T, lossType );
    [A, B, C, D] = tmmCylCone( ra(n), ra(n+1), L(n), Gamma, Zc );
    Zl = (A.*Zl + B) ./ (C.*Zl + D);
  end
  
  if isHole(n)
    Gamma = sectionLosses( rb(nHole), rb(nHole), 0, f, T, lossType );
    [A, B, C, D] = tmmTonehole( rb(nHole)/ra(n), rb(nHole), t(nHole), ...
      states(nHole), Gamma, '', T, chimney(nHole), padr(nHole), ...
      padt(nHole), holew(nHole) );
    nHole = nHole - 1;
    Zl = (A.*Zl + B) ./ (C.*Zl + D);
  end
end

if ra(1) ~= ra(2) % recalculate Zc for input conic section
  [c, rho] = thermoConstants( T );
  Zc = rho * c / ( pi * ra(1) * ra(1) );
end
Zin = Zl ./ Zc;