You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: dbtophon.m
    path of file: ./repos/Emotional-Video-to-Audio-with-ANFIS-DeepRNN/scripts/features_from_sound/utils
    
    the code of the file until where you have to start completion: %
% FILE NAME: DBTOPHON.M
%
function P_XX = dbtophon(Ci)
% CONVERT SPREAD BARK SPECTRUM INTO PHON SCALE
% load a:\MBSD\equal.mat % EQUAL-LOUD
    
function P_XX = dbtophon(Ci)
% CONVERT SPREAD BARK SPECTRUM INTO PHON SCALE
% load a:\MBSD\equal.mat % EQUAL-LOUDNESS CONTOURS
n=length(Ci);
T = 10*log10(Ci); % COMPUTE BARK 4 TO 18 ONLY IN dB
    for i = 1:1:n
       [I]=find(T(i)<=equalcon(:,i));
       if min(I)==1
           P_XX(i)=phons(1);
       else
           t1 = (T(i) - eqlcon(j-1,i))/(eqlcon(j,i) - eqlcon(j-1,i));
           P_XX(i) = phons(j-1) + t1*(phons(j) - phons(j-1));
       end