public class EntityNoisestorm extends EntityAnimal
{
    public EntityNoisestorm(World par1World)
    {
        super(par1World);
        this.setSize(0.9F, 1.3F);
    }

    @Override
    protected void applyEntityAttributes()
    {
        super.applyEntityAttributes();
        this.getEntityAttribute(SharedMonsterAttributes.maxHealth).setAttribute(10.0D);
        this.getEntityAttribute(SharedMonsterAttributes.movementSpeed).setAttribute(0.20000000298023224D);
    }

    @Override
    protected String getLivingSound()
    {
        // return "yourmod:YourSound";//this refers to:yourmod/sound/YourSound
    }

    @Override
    protected String getHurtSound()
    {
        // return "yourmod:optionalFile.YourSound";//this refers to:yourmod/sound/optionalFile/YourSound
    }

    @Override
    protected String getDeathSound()
    {
        // return "yourmod:optionalFile.optionalFile2.YourSound";//etc.
    }

    @Override
    protected float getSoundVolume()
    {
        return 0.4F;
    }
}

Create EntityNoisestorm.java