# How to state the PSD value (random vibration)

In random vibration analysis, the load is given as a PSD (power spectral density). The values are often $$G^2/Hz$$, but I have an example where the PSD is a pressure $$Pa^2/Hz$$. The value is written as $$(100 N/m^2)^2/Hz$$ which brings me to these questions:

1. Is that value $$(100 \;N/m^2)^2/Hz$$ equal to $$10000 \;(N/m^2)^2/Hz$$? (The results of the analysis imply that the answer is Yes, but I want to confirm my understanding.)
2. Are both styles of writing the value acceptable? Is one style more common or acceptable than the other? For example, I have never seen an acceleration PSD written as $$(5 \;G)^2/Hz$$ to represent a value of $$25 \;G^2/Hz$$.
• I would guess they are using $\text{hPa}^2/\text{Hz}$ in their application because $100\text{N}/\text{m}^2 = 1 \text{hPa} = 1 \text{mbar}$. – alephzero Apr 26 '19 at 15:04
• just a question, in the first case, G2/Hz, how do you insert it in a simulation software to replicate? – FabioSpaghetti Aug 28 '19 at 11:27