Brain response frequencies while sleeping
Sleep as you may know is divided into 2 broad categories which are the REM (Rapid Eye movement) and NREM (non rapid eye movement). NREM is further divided into 3 stages (reference). You never know which stage of sleep you are in when you are subjected to a particular frequency of sound. Your response to different sounds differ in your different sleep cycles. 

The present 3 stages in NREM sleep is an update by The American Academy of Sleep Medicine (AASM) in 2007 (reference).The original 4 stages in the Rechtschaffen and Kales (R&amp;K) standardization of 1968 (reference) has been used to explain the effect of disturbances in different sleep cycles


  Stage 1 is still the phase of sleep from which it is easiest to wake
  someone up.
  
  People in Stage 2 sleep are unlikely to react to a light or a noise,
  unless it is extremely bright or loud.
  
  During Stage 3, the muscles still have some tonus, and sleepers show
  very little response to external stimuli unless they are very strong
  or have a special personal meaning (for example, when someone calls
  your name, or when a baby cries within earshot of its mother). 
  
  Stage 4 is the stage of sleep that accomplishes most of the body’s
  repair work and from which it is most difficult to wake someone up (reference).


A study conducted to measure brain activity while sleeping subjects were subjected to varying degrees of sound found that some people did you wake up after being hit with 70db of sound while others woke up even at sounds between 40 - 50 db (reference). This could lead to new behavioral or drug therapies for people with sleep disorders.  

A review on the affect of low frequency sound on sleep could not reach any significant conclusions warranting that more search needs to be conducted in the field.(reference).

You will be interested to know that different sounds have been found to wake up men and women. A list is available here. Differences between the sleep of men and women are listed in this article.