Sound Level test with Swept sine is error!! help

[chipie]

I use the example program "SVXMPL_Swept Sine FRF(DAQmx).vi" to test the frequency response of my DUT. Some frequencies whose level should lower than -40dBV,  tested with "SVXMPL_Swept Sine FRF(DAQmx).vi", their sound level is higher than -40dBV.

If use " SVXMPL_One Shot Gain and Distortion(DAQmx).vi" to test the frequency response one by one, the sound level is right.

I guess there are some error in the Swept sine toolkit or my setting is error. I have try my best to use the same setting when using the two VIs. Following is the setting comparision:

SVXMPL_Swept Sine FRF(DAQmx).vi                                  SVXMPL_One Shot Gain and Distortion(DAQmx).vi        
amplitude input:   51.2mV                                                       amplitude input: 51.2mV
propagation time [samples]: 108                                            propagation time [samples]: 108
sampling frequency [Hz]:50000HZ                                         sampling frequency [Hz]:50000HZ (set with "svx_override_DAQmx

                                                                                                                                                         Parameters.vi")
block duration [ms]: 500ms                                                    block size: 25000 (set with "svx_override_DAQmx Parameters.vi")
settling time:100ms                                                                settling time:100ms
settle cycles:10                                                                       settle cycles:10
integration time [s]:100ms                                                      integration time [s]:100ms
integration cycles:10                                                               integration cycles:10
sweep frequencies [Hz]:                                                         frequency [Hz]:100HZ
start freq=100HZ
stop freq=100HZ
number of steps=1

The output sound level of the two VI is:
SVXMPL_Swept Sine FRF(DAQmx).vi                                   SVXMPL_One Shot Gain and Distortion(DAQmx).vi
-38dBV                                                                                     -41.79dBV  

I found the time Record of "SVXMPL_Swept Sine FRF(DAQmx).vi" is abnormal, pls find the attached picture "swept.png", there are abnormal higher signal at the start and stop terminal. which caused the sound level lower than -40dBV can't be test rightly. However, the time record picture one-shot.png of "SVXMPL_One Shot Gain and Distortion(DAQmx).vi" is normal.  

Can't anyone help me?! Why one shot test and swept sine test at one frequency are different?