A method comprising applying ultrasonic energy to a biomass to alcohol production process is provided. In one embodiment the alcohol production process is an ethanol production process. In one embodiment, the biomass to alcohol process employs ultrasonic energy as the only means of pretreatment. In one embodiment, the biomass to alcohol process additionally employs a concentrated acid hydrolysis pretreatment. In one embodiment, the biomass to alcohol process additionally employs any conventional pretreatment, such as a hydrothermal or chemical pretreatment, followed by an enzymatic hydrolysis step or a simultaneous enzymatic hydrolysis and saccharification step. In one embodiment, the conventional pretreatment is selected from the group consisting of dilute acid hydrolysis, high pressure hot water-based methods, i.e., hydrothermal treatments such as steam explosion and aqueous hot water extraction, reactor systems (e.g., batch, continuous flow, counter-flow, flow-through, and the like), ammonia explosion, ammonia recycled percolation (ARP), lime treatment and a pH-based process.