Brake pedal pulsates and hisses when brakes applied

I noticed today when I hit the brakes pedal in my car it started to pulsate\vibrate and when I have the car in neutral (manual trans) and I hold the brake I hear a hissing sound. Could this be a master cylinder issue? My car has 97000 miles on it and I don't know if this is a common issue or just parts becoming weak.

I did bleed the brakes about 6 months ago, maybe I should bleed the again and see what happens.

Any advice would be awesome. Thank

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