The FRFs attached definitely do not look as they should. What are all these peaks present?

[4445]

I am using Labview 8.5, Sound and Vibration 6.0, NI 9233 USB, Triaxial DeltaTron Accelerometer Type 4524, Impact Hammer Type 8206,(Bruel and Kjaer) and cantilever beam to conduct an impact hammer test to obtain FRF solution. As shown in impact waveform attached double impacts or more are present. How can I make sound and vibration use only the first impact and exclude the remaining in obtaining the FRF. The FRFs attached definitely do not look as they should. What are all these peaks present?

[DFGray]

At a guess, it appears your hammer is bouncing, but without actually looking at your hardware, it would be difficult to say definitively.

You can use Subset and Resample to slice out a piece of your waveform, but that will probably effect your frequency response, as well.

However, I am not an expert in sound and vibration, so will see if I can get someone who is to respond. 

[dsb@NI]

Dr. Gray is right - if you take a subset, it will affect your measured frequency responses because you will also need to chop the responses (likely before the response decays to ~zero).

It may be difficult, but the the best solution is to eliminate the double hits:

1. Practice impacting technique (use an automatic impactor if necessary)
2. Change impact location (if you are currently striking the tip, striking closer to the base makes it easier to avoid double hits)
3. Switch impact and response locations
4. Do whatever it takes to achieve a clean hit

Also, configure the pretrigger in the Trigger Step to make sure that you capture the entire impact.