Problem with Continuous Swept-Sine THD and limit testing

[Houssem95]

Hello ,

I am testing a loudspeaker using NI PXI 4461 and "sound and vibration " suite  .

The loudspeaker in linked to the output of the card that is generating a continuos sine sweep  ( 20hz to 20Khz) and getting the signal back through a microphone that is linked to the input of the 4461 . Sampling rate : 51.2KHz ; Delay :108

I used the VI example " Continuous Swept-Sine Measurements (DAQmx) "  and modified it a little bit .

I want to compare the THD values calculated with the "SV Continuous Swept-Sine THD VI" with golden values that have already been measured . 

My problem is that when I want to use the SV limit testing VI , to compare THD to the golden values , the limit testing VI needs to have the same X-axis ( frequency) for the THD and for the golden values , which is impossible because there is almost 20000 frequency component of the THD and the frequencies are very bizarre as you will see in the photo ( I can't use searching for my values in the THD array ,) .

So , Is there a solution  so I can compare the THD with my values ?  and how does the "SV Continuous Swept-Sine THD VI" work ? 

I am sorry for the messy code . ( LV 2018 )

[Gaheel17]

Hi!

I have some questions:

1. Can you clarify what do you use to measure the golden values?

2. How many golden values do you have?

3. Is there a continuous spacing between the frequencies of the golden values?

Also, do you see any value on comparing the THD of values at different fundamental frequencies?

Best,

Gaheel17

[Houssem95]

Hello  and thank you for your response  :

1 - I do not know , they were just sent to me, They were  propably calculated while testing golden loudspeakers . 

2- 30

3- The frequencies of the golden values were the result of 1/3 octave of the input signal . You can find the frequencies of the golden values in the image "golden" that  I attached to the first post .

Yes , I think there is a value to know how the loudspeaker behaves regarding distorsion , for the whole frequency range ( 20 to 20Khz ) . I am new to acoustics , the opinion of an expert would be more efficient . 

Best regards .