Photoinduced enthalpic and structural volume changes can be estimated taking advantage of the different dependences that the signals arising from the structural volume changes and the heat release have.
As explained in detail in the phenomenological theory, the overall signal can be written as

Aqueous solutions
In water and dilute aqueous solutions, the variation of b/C_pr is obtained by varying the temperature of the solution, taking advantage of the strong temperature dependence of this parameter. Experiments are generally done in a small temperature range (e.g., 5 - 30 °C). A prerequisite is that the temperature does not significantly affect the kinetics of the various processes. The ratio (C_pr /b )T for neat water is obtained from tabulated values. In particular, b_water = 0 at 3.9 °C (T_b=0), is positive above and negative below this temperature. At T_b=0 , heat release gives rise to no signal. This peculiar feature allows the straightforward assessment of the existence of structural volume changes. For aqueous solutions containing salts or other additives at mM concentrations or higher, (C_pr /b )_T and T_b=0 must be determined by comparison of the signal obtained for a calorimetric reference in the solvent of interest and in water.
Two methods have been proposed to separate the enthalpic (a_i) and the volumetric (DV_R,i).  These methods  take advantage of the temperature dependence of b/C_pr for aqueous solutions and have been termed the several temperatures (ST) method and the two temperatures (TT) method.
In the ST method, the reference and the sample signals are measured at several temperatures and a_i and F_i DV_R,i are obtained as the intercept and the slope of the linear plot of j_i vs C_pr/b. The structural volume change can be estimated with good accuracy, whereas the enthalpic information is generally affected by larger errors due to the unfavourable propagation in the linear regression. Typical errors are 0.1 ml/mol on F_i DV_R,i whereas on the enthalpic change it is common to have errors as large as 2 kcal/mol.
In case the main goal is the determination of the structural volume change, the TT method may be applied. Essentially, the photoacoustic wave is measured for the sample at T_b=0 and at a slightly higher temperature T_b¹0 for which b ¹ 0. The parameters DV_e,i/E_l and a_i are then calculated as follows:
 
 DV_e,i = j_i(T_b=0) (b/C_pr) E_l
 
a_i = j_i(T_b¹0) - j_i(T_b=0)
 
These equations only hold for values of T_b=0 and T_b¹0 which are near, such that the risetime of the LIOAS signal and the compressibility of the solution are similar. The signal of the reference at T_b¹0 is used together with that of the sample at T_b=0 and at T_b¹0 to obtain the values of j_i(T_b=0) and j_i(T_b¹0). A time shift of the sample waveform with respect to the reference waveform at T_b¹0 is necessary to compensate for the change in the speed of sound that leads to a slightly different arrival time at both temperatures. Thermal instability of the sample holder and trigger arrival fluctuations make the shifting an important option in the fitting routines.