I think firstly You need to find a scale in the journals. If you don't find, you can create your own scale. However, in order to create a scale, you need to find conceptual dimensions and you need to create a questionnaire. After creating it, at least 32 people need to fill your questionnaire, because normality in the statistics is important. Then, confirmatory and exploratory factor analysis should be applied through SPSS and Lisrel..
What an interesting question. My own work on silence has been qualitative and suggests a cultural difference in how silence is accomplished and what it means. I wonder if some of the research on whistle blowers might be helpful. Whistle blowing is the opposite of the two types of silence you mention in your post, so the measures used in those studies may be helpful as you create your own measure of silence.
Nice topic Farhad. First of all, I think there is no absolute silence in organizations. Voice just takes place in different organizational setting in the dark behind closed doors or at water cooler.
You might look into the literature on Voice and Dissent. I highly recommend Jeffrey Kassing work on Dissent, he published a book " Dissent in Organizations" and wrote many papers with empirical field work too. He divides dissent / voice to three types:
1. Upward dissent ( issues voiced in the open to the management )
2. Latent/Lateral dissent ( issues voices to peers and remain in the dark) which can be considered as a from of silence.
3. Displaced dissent/Whistle blowing ( vice to the outside world) which I think is an indicator of the tipping point for silence when it spills over to the general public beyond the organizational boundaries.
I built a System Dynamic model of his work on Dissent ( the upward and the latent only) and I coined a term "Perceived Management Tolerance for Dissent" that is quantified as the ratio of upward dissent to the ignored, dismissed, and latent dissent.
perceived management tolerance to dissent=(Upward Dissent)/(Dismissed Dissent+Ignored Dissent+Latent Dissent)
where low values of the above term suggests low values of Upward Dissent or greater levels of ignored, dismissed, and latent dissent and drives upward dissenters to become latent dissenters ( silent).
I am attaching a working paper for my work that is currently being prepared for publishing and hope this helps.