第3回 Tension #3

インハーモニシティと同じく キー番号と弦長と番手（又は弦径）から

>> getTension(49, 390, 16.5)
ans = 66.831

弦の張力を計算します。

function [gten, ten] = getTension(key, leng, ban)
  SM = 7.85;          # 芯線密度 g/cm^3
  NG = 9.80665204821; # 重力加速度 kgw
  mm = 1000;

  [dia, pitch] = GetDia(ban);
  freq = GetFreq(key, pitch);

  ten = pi*SM*mm*freq^2*(leng/mm)^2*(dia/mm)^2;
  gten = ten/NG;
end

function [dia, aa] = getDia(bante)
  ba = 12:0.5:25;
  dm = 1.25:0.05:1.500;
  da = 0.725:0.025:1.225;
  di = [da dm];

  dia = -1;
  aa = 440;

  if (bante < 12 && bante > 0.1)
    dia = bante;
    aa = 415;
  else
    x = find(ba == bante);
    if (x > 0)
      dia = di(x);
    end
  end
end # 番手から弦径を得ます

function freq = getFreq(key, pitch)
  freq = pitch .* 2.^((key-49)./12);
end # キー番号から周波数を算出します