I apologize, but without specific information about the sleep study you're referring to, I cannot provide precise details about the sound pressure levels used in that particular study. There are numerous sleep studies conducted worldwide, each with its own methodology and parameters.
In general, sleep studies comparing responses to windfarm and road traffic noise samples would typically involve measuring sound pressure levels at various points. The specific sound pressure levels used in such studies can vary depending on the research design, location, and objectives of the study.
To obtain accurate information regarding the sound pressure levels used in a specific sleep study comparing responses to windfarm and road traffic noise samples, I would recommend referring to the original research publication or contacting the researchers directly for precise details.