What does the author mean by 'deodorisation'?

Directions: Read the following passage and answer the question based on the passage.

PASSAGE – III:

The moral conditions of the operatic stage are no doubt far more satisfactory than they were, and in England the general deodorisation of the theatre has not been unfelt in opera; but even without the unworthy motives which too often drew the bucks and the dandies of a past day to the opera-house, the influence of the unintelligent part of the audience upon the performers is far from good in an artistic sense. It is this which fosters that mental condition with which all who are acquainted with the operatic world are only too familiar. Now, just as in the days when Marcello wrote his Teatro alla moda, there is scarcely a singer who does not hold, and extremely few who do not express, the opinion that all the rest of the profession is in league against them; and by this supposition, as well as by many other circumstances, an atmosphere is created which is wholly antagonistic to the attainment of artistic perfection. All honour is due to the purely artistic singers who have reached their position without intrigue, and whose influence on their colleagues is the best stimulus to wholesome endeavour. It is beyond question that the greater the proportion of intelligent hearers in any audience or set of subscribers, the higher will the standard be, not only in vocalisation, but in that combination which makes the artist as distinguished from the mere singer.

For every reason, too, it is desirable that opera should be given, as a general rule, in the language of the country in which the performance takes place, and although the system of giving each work with its own original words is an ideally perfect one for trained hearers, yet the difficulties in the way of its realisation, and the absurdities that result from such expedients as a mixture of two or more languages in the same piece, render it practically inexpedient for ordinary operatic undertakings. The recognition of English as a possible medium of vocal expression may be slow, but it is certainly making progress, and in the last seasons at Covent Garden it was occasionally employed even before the fashionable subscribers, who may be presumed to have tolerated it, since they did not manifest any disapproval of its use. Since the first edition of this book was published, the Utopian idea, as it then seemed, of a national opera for London has advanced considerably towards realisation, and it is certain that when it is set on foot, the English language alone will be employed.

While opera is habitually performed in a foreign language, or, if in English, by those who have not the art of making their words intelligible, there will always be a demand for books that tell the story more clearly than is to be found in the doggerel translations of the libretti, unless audiences return with one accord to the attitude of the amateurs of former days, who paid not the slightest attention to the plot of the piece, provided only that their favourite singers were taking part.