Investigating correlation for unequal signal lengths
If you are using MATLAB, there is a built in object type, called 


  timeseries


, that is very useful for this sort of problem.

&gt;    Methods for class timeseries:
&gt; 
&gt; addevent              getabstime            gettsbeforeatevent    mean
&gt; pvset                 times                  addsample            
&gt; getdatasamples        gettsbeforeevent      median               
&gt; rdivide               timeseries             append               
&gt; getdatasamplesize     gettsbetweenevents    min                  
&gt; resample              tsprops                createTstoolNode     
&gt; getinterpmethod       hasduplicatetimes     minus                 set 
&gt; utArithCommonData      delevent              getprop              
&gt; idealfilter           mldivide              setabstime           
&gt; utArithCommonOutput    delsample             getqualitydesc       
&gt; init                  mode                  setinterpmethod      
&gt; utArithCommonTime      detrend               getsamples            iqr
&gt; mrdivide              setprop               utChkforSlashInName   
&gt; display               getsampleusingtime    isequal              
&gt; mtimes                setuniformtime        utGetEventTime         eq 
&gt; gettsafteratevent     isequalwithequalnans  plot                  std 
&gt; utStatCalculation      filter                gettsafterevent      
&gt; ldivide               plus                  sum                   var 
&gt; get                   gettsatevent          max                  
&gt; pvget                 synchronize           
&gt; 
&gt; Static methods:
&gt; 
&gt; loadobj               tsChkTime             tsgetrelativetime


The setuniformtime method will do the interpolation for you. The other methods are often useful.