The present invention relates to the use of a -\u03b2-D-glucan as an emulsion stabilizer. Such a composition is clear in appearance, and stable. The present invention has found that the dynamic range of an EDFA can be significantly increased by using pulse width modulation to pulse pump current at or near the minimum current stability threshold, in order to produce lower power output. When the maximum variation width of the threshold voltage for memorizing information is larger, since stress to a memory cell owing to a rewrite operation of memory information becomes larger, it is inferior In a point of guaranteeing the number of times of rewrite operation; however, since a read current becomes larger, a read speed of memory information can be expedited. An exhaust system and a method for muffling sound therein are also provided.