BARWICK C.J. The appellant was employed by the respondent Commissioner for a railway workshops at Eveleigh, Sydney. It is conceded that this involved him in working in conditions of intense noise and that as a result he suffered from perceptive deafness in each of his ears, a condition commonly known and referred to in the Workers' Compensation Act, 1926-1965 (N.S.W.) (the Act) as "boilermaker's deafness". He applied for a lump sum of compensation as provided for in s. 16 of the Act. (at p218)

2. The extent of his loss of hearing due to boilermaker's deafness was contested by the respondent before the Workers' Compensation Commission (the Commission). After hearing the evidence of three medical men specializing as otologists, the learned Commissioner found that the applicant had lost hearing to the extent of thirty-one decibels in his left ear and thirty decibels in his right ear; that is to say, that the average minimum noice level to which the applicant could respond through a series of frequencies embraced within the frequency range experienced in daily life and communication was measured as thirty-one and thirty decibels respectively. The medical evidence was not in difference to any significant degree on these figures which resulted from the use of an audiometer in the hands, mostly, of a technician. (at p219)

3. But to apply the Act, it is not enough to have the measure of the loss of hearing; it is necessary to express that loss as a percentage of impairment of hearing (see table to s. 16). That is to say, the absolute loss must be expressed as a comparative loss. It was the performance of this function that gave rise to the dispute in this case. The Commissioner found that the percentage loss of hearing of the applicant was nineteen per cent in relation to his left ear and eighteen per cent in relation to his right. This finding accorded with that of a medical board to which the applicant had been referred pursuant to s. 51 (8). But, the finding of that board was not conclusive, s. 51 (5). (at p219)

4. Again, there was no dispute before the Commission that, if the loss of hearing were taken at thirty-one and thirty decibels respectively, the percentage of impairment would be as found by the Commission. But the medical witnesses for the defence asserted that because of the age of the applicant, namely sixty years at the date of his application for compensation, he would then, in any case, have suffered a loss of perceptive hearing due to presbycusis (the medical description of the ageing process in relation to perceptive hearing). This claim they founded not upon any examination of the applicant nor upon any circumstance connected with him, his health, or his manner of life: but simply upon the recorded findings of workers in this particular field of medicine who concluded that on an average, perceptive hearing declined by 0.5 decibels for each year of age beyond fifty. (at p219)

5. The Commissioner expressed himself on this aspect of the matter as follows:

"His (the appellant's) evidence shows that on 10th May

1966, (the date of his application for compensation) he was

sixty years of age and, if he was like the general run of men,

very likely to have a hearing loss through presbycusis of

something like five decibels over the range of conversation tone

frequencies. There is nothing in the evidence that inclines me

to put him out of the general run. If the onus lies on him

to show I should, he has not discharged it."

It is noticeable that the Commissioner did not say what he would have found positively had he thought the onus as to this fact was upon the respondent. (at p219)

6. The evidence before the Commission made it clear, and the Commissioner found, that "qualitatively hearing loss from presbycusis and from boilermaker's deafness are indistinguishable". Consequently, not only was there no evidence derived from physical examination of him, but such an examination could not have determined whether or not the appellant had suffered any loss by presbycusis. The statutory assumption is that the worker suffering from boilermaker's deafness is to be treated, for the purposes of s. 16 and the assessment of compensation, as if the loss of hearing had happened at one blow at the time the worker makes his claim for compensation. Here, as I have said, it is conceded that the appellant had a loss of hearing, boilermaker's deafness, due to his employment with the respondent. His actual loss of hearing measured as at the date of his application for compensation was as the Commission found, thirty-one decibels as to one ear and thirty decibels as to the other. Quite clearly, in my opinion, there is nothing of a direct evidentiary nature to establish that in point of fact any part of this loss was due to any other cause than the industrial employment. (at p220)

7. However, two matters were pressed upon the Commission as warranting the conclusion that some part of that loss was attributable to presbycusis, namely, that according to technical journals on an average humans lose hearing to the extent of 0.5 decibels for each year of their age beyond fifty and that an endorsement upon a table prepared by the Commonwealth Acoustic Laboratories tendered in evidence namely, "Presbycusis: 0.5 decibel C.A.L. average hearing loss for every year above fifty years of age" indicated that before applying the table a deduction should always be made for an assessed amount of hearing loss due to presbycusis in accordance with the average as stated and the age of the person in respect of whose hearing loss the table is used. (at p220)

8. The hearing impairment table published by the Commonwealth Acoustic Laboratories is little more than an arithmetical table converting the absolute loss of hearing into a percentage of impairment of hearing. But, for this purpose a choice had to be made on the one hand of what would be considered normal, and, on the other hand, of the point which for practical purposes would be taken as a total loss of hearing. Within these limits, a comparison between these norms and the actual loss of hearing detected by the examination could be expressed as a percentage of impairment of hearing. The Commonwealth Acoustic Laboratories accepted - and the medical evidence in the case agreed - that until a person lost or lacked hearing to the extent of more than fifteen decibels from any cause, he or she would be regarded as having normal hearing. It was similarly accepted and medically agreed in the evidence that when hearing is lost to the extent of 100 decibels, the person can be regarded for practical purposes as completely deaf. Between fifteen and 100 decibels, therefore, is the range of loss of hearing which has significance for practical, and certainly for industrial and compensatory purposes. A loss of one decibel within this range arithmetically must represent 1.2 per centage impairment of hearing. (at p221)

9. In my opinion, the note which is endorsed on this table and which I have already quoted in full, is completely disparate to the purposes of the arithmetical table. It is, of course, informative, just as are the examples given at the foot of the table as to the method of arriving at an average hearing loss. It seems to me that so far as the arithmetical conversion is concerned, it can make no difference that a loss of hearing to the extent, for example of ten decibels has been suffered due to presbycusis or to any other cause. There is no relevant impairment of normal hearing. As I have said, that conclusion all the medical evidence in the case would support. (at p221)

10. But of course, if it is possible to decide that there has been in fact a loss of hearing due to a cause irrelevant to the purpose for which compensation is being assessed, that loss of hearing could be excluded from the calculation of the relevant loss of hearing before its arithmetical conversion to a percentage of impairment of hearing is attempted if it was a loss which rendered the hearing abnormal. But, the endorsed note cannot, in my opinion, mean that in the case of every person over the age of fifty years an automatic deduction is to be made for presbycusis from the total loss of hearing ascertained on examination. There was some evidence that some medical practitioners treated the table as requiring such an exercise: but, in my opinion, they were mistaken as to the purpose of the endorsed informative note. (at p221)

11. I should, however, deal with the question whether the Commission would have been warranted in treating the appellant as in fact having lost hearing due to presbycusis simply because it was said in the otological writings that humans on the average lose perceptive hearing due simply to an ageing process so soon as they pass fifty years of age. In my opinion, this statistical average does not warrant the conclusion - which would be the only relevant conclusion - that the appellant in fact had lost hearing due to presbycusis, or that, but for the onset of boilermaker's deafness he would have suffered such a loss by the time of his application for compensation. The first conclusion of fact therefore is, in my opinion, not made out. The second conclusion, even if contrary to my own view it could be drawn would, in my opinion, be clearly irrelevant to the matter in hand. It cannot be an answer to a workman suffering an injury that he would probably in any case as he got older suffer an injury of a like but lesser kind. (at p222)

12. The statutory assumption raises of necessity a somewhat artificial situation. We know that the appellant's deafness was probably of long standing and not, as the statute would have us assume, an occurrence of a moment of time. Medical evidence in the case suggested that in the case of a boilermaker there is progressive impairment of hearing in the early years of employment followed by a "plateau" of at most little further degeneration in perception followed again in later life if exposure to the industrial noise persists by another phase of accelerated impairment. It is thus fairly clear that loss of hearing of the same kind due to the passing years is neither detectable nor measurable. Whether the afflicted boilermaker does suffer from presbycusis is, of necessity, unknown. When he reaches fifty years of age he no longer has normal hearing. When the statute intervenes and imposes its artificial approach to the identification of the injury such a hypothetically possible loss (if indeed medical science goes so far) must, in my opinion, be irrelevant. In my opinion, there was here no material on which any part of the measured loss of hearing could be found in fact to be due to other than boilermaker's deafness. (at p222)

13. Before parting with the case, I ought to add a word as to the onus of proof of the existence of a loss of hearing from a noncompensable cause. Reference is made in one of the judgments delivered in the Supreme Court to Watts v. Rake (1); Purkess v. Crittenden (2) and to Darling Island Stevedoring and Lighterage Co. Ltd. v. Hankinson (3). In my opinion, the reasoning of the earlier of these cases is quite apposite when it is asserted that an applicant for lump sum compensation under s. 16 already had an impairment of hearing, due to causes other than his industrial occupation. It is not it seems to me for the applicant to negative, for example, that he had been subject to presbycusis. That he had already suffered a loss of hearing from a non-compensable cause is a matter of fact which, in my opinion, the employer must establish. The statute as it seems to me warrants the Commission in treating the actual loss of hearing ascertained by examination as at the date of the application under s. 16 for compensation as being wholly due to the industrial occupation, once it is established that the worker is on that date suffering from boilermaker's deafness. If the employer claims that some identifiable part of that loss of hearing is due in fact to some other cause, it must rest on the employer to do so. (at p223)

14. In my opinion, there was ample evidence on which the Commissioner could take the course he did and none that required him to take the course favoured by the majority of the Supreme Court. The appeal should be allowed and the award of the Commission reinstated. (at p223)

MCTIERNAN J. I am of the same opinion as the Chief Justice and agree with his Honour's reasons. (at p223)

MENZIES J. Having read the whole of the evidence upon which his Honour Judge Ferrari, as a member of the Worker's Compensation Commission of New South Wales, made an award in favour of a worker claiming compensation for boilermaker's deafness on the footing that the worker had suffered nineteen per cent diminution of hearing in his left ear and eighteen per cent diminution of hearing in his right ear, I have come to the conclusion that the Court of Appeal of the Supreme Court was wrong in deciding that there was no evidence to support these particular findings. It seems to me that, apart from anything else, there was in the report of the medical board precise evidence to support the findings that were made. The medical board's report was as follows:

"Following upon the Commission's direction herein dated

19th October 1966, in terms of s. 51 (8) of the Workers'

Compensation Act, 1926, as amended, we hereby report as

follows:

1. Does the applicant suffer from permanent loss of hearing

from any cause of each ear: and if so, what is the nature

of the hearing loss and percentage loss of hearing of each ear?

Yes

L. Ear=19%

R. Ear=18%

2. Does the applicant suffer from permanent loss of hearing

of each ear of the nature of boilermaker's deafness : and

if so, what is the percentage of hearing loss of each ear of

this nature?

Yes

L. Ear=19%

R. Ear=18%

3. In assessing any hearing loss referred to in the Board's

answer to question 2 has the Board considered it necessary

to make an allowance for loss of hearing due to any

condition other than boilermaker's deafness, including

presbycusis: if so, what condition or conditions?

No."

There was other medical evidence to the same effect. (at p224)

2. At the same time, in common with the majority of the Court of Appeal, I cannot be wholly satisfied with the use that the learned judge made of Ex. 2 which was an extract from the Journal of the Oto-Laryngological Society of Australia. It seems to me that the following note : "Presbycusis : 0.5 decibel C.A.L. average hearing loss for every year above fifty years of age" is directed to the adjustment of the first column of the table which is headed "C.A.L. Average Hearing Loss (db)" so that in applying the table to a sufferer above the age of fifty a loss of 0.5 decibels for each year above fifty is to be attributed to presbycusis so that, for instance, when the C.A.L. average hearing loss is thirty-five in a man of sixty, the table should read as though five decibels of loss resulted from presbycusis so that the table would be applied with an average hearing loss of thirty decibels instead of thirty-five decibels. In other words, it seems to me that the note is simply directed to the way in which the table should be used in relation to a person above fifty years of age. (at p224)

3. Accordingly, I think his Honour was correct in saying as he did:

"His" - i.e. the worker's - "evidence shows that on 10th

May 1966, he was sixty years of age and, if he was like the

general run of men, very likely to have a hearing loss through

presbycusis of something like five decibels over the range

of conversation tone frequencies. There is nothing in the

evidence that inclines me to put him out of the general run.

If the onus lies on him to show I should, he has not discharged

it. . . . I find that the applicant had about the average five

decibels of hearing loss from presbycusis, so that he had that

much less hearing to lose on 10th May 1966 and that his loss

from boilermaker's deafness on 11th May 1966 was that

much less than his total actual hearing loss. . . . I accordingly

allocate the applicant's hearing losses of thirty-one decibels

in the left ear and thirty in the right as to five decibels of each

as lost before the employment injury on 11th May 1966 and

as to the residue as lost by it on that date." (at p224)

4. However, as I understand the extract, his Honour was not correct in going on to say as he did:

"If I apply the table to this applicant's deemed condition

under the Act before and after the injury of 11th May, 1966,

before it he had five decibels=nil percentage loss of hearing,

and after it he had a loss of left thirty-one and right thirty

decibels, to the nearest whole figures nineteen per cent and

eighteen per cent respectively." (at p225)

5. With respect, it seems to me that upon his Honour's earlier findings his calculation according to the table of the percentage of lost hearing due to boilermaker's deafness should have been on the basis of twenty-six and twenty-five decibels loss rather than thirty-one and thirty decibels loss to produce a percentage loss of 12.9 and 11.8 rather than nineteen and eighteen as found. In view of his earlier findings I do not understand his Honour's statement - which I take to be a criticism of so calculating the percentage loss - that:

"This procedure treats the employment injury as having

cured the applicant of his presbycusis. It does not measure

the effect of the employment injury on Mr. Sadler; it measures

its effect upon someone else who had ideally perfect hearing." (at p225)

6. However, whether I am right or wrong about this, I think that there was evidence that the percentage loss was nineteen and eighteen as found and that, if his Honour made an error, it was not an error in point of law to justify the setting aside of his award. (at p225)

7. Accordingly, I would allow the appeal. (at p225)

WINDEYER J. I agree that this appeal should be allowed. There was, in my view, evidence on which the learned judge of the Workers' Compensation Commission of New South Wales could reach the conclusions he did in his carefully considered judgment. (at p225)

2. I do not see why the "loss of hearing" which the appellant suffered as a result of boilermaker's deafness caused by seventeen years' work in the railway workshops was to be measured against an unverifiable assumption of what his hearing might have been on 11th May 1966 had he spent his time in some quiet pursuit. Section 16 of the Workers' Compensation Act, 1926 (N.S.W.), as amended up to the date of the hearing before the Commission, provides - s. 16 (1A) - that the appellant's loss of hearing was, for the purpose of determining his right to the amount shewn in the table in the section, to be deemed to have happened on 11th May 1966, when he made his claim for compensation. His claim was for a partial loss of hearing of each ear. The award, made by his Honour pursuant to s. 16, was expressed to be "for $304 in respect of nineteen per cent diminution of hearing of left ear and for $288 in respect of eighteen per cent diminution of hearing of right ear resulting from injury deemed to have happened on 11th May 1966". In the course of his judgment the learned judge, speaking of the provision of s. 16 and the table there, said:

"The measure of diminution of hearing is . . . an objective

one, the same for all workers, young and old, professional,

skilled or labourer. It is, however, a measure personal to

the injured worker in the sense that the dininution concerned

is the diminution of his hearing, to be ascertained by measuring

his remaining hearing against the hearing he actually had

before the injury, and not as against the hearing he was born

with, or that of his fellow workers or of the perfect man or

the average man."

I think that statement is, as a general proposition, correct. It applies to a partial loss of hearing of an ear. The note which appears in the statute provides that in such a case "there shall be payable such percentage of the amount that would be payable for the total loss of the hearing thereof as is equal to the percentage of the diminution of hearing". But his Honour's proposition obviously applies only in cases of a partial loss, as this is. It is not, I consider, applicable to total loss of hearing - either of one ear or of both ears. If a man be made totally deaf he is to be fully compensated for loss of hearing: and it is, I think, immaterial that he may have been hard of hearing before the event which made him deaf. It is the same with total loss of sight: compensation is payable on the basis of blindness. It matters not whether the worker before he was blinded had had acute vision or poor vision, whether he wore spectacles or did not - except in cases within s. 16 (5A) enacted in 1966. The idea of "diminution" has no place in cases of a total loss. In a case, such as the present, however, the statute requires diminution of hearing to be counted. But counted against what? Against I assume the hearing which the worker had which was impaired in his employment. But this is not to be assumed to be such hearing as he might have had on an arbitrarily chosen and artificial date, when perhaps some other cause such as increasing age might have made him hard of hearing. Certainly the appellant's partial deafness was deemed to have happened on 11th May. But this does not mean that, in looking to cause and result, we are to desert reality and proceed as if the appellant's disability had been caused suddenly on that date. His hearing on 11th May is not to be measured against his hearing on the day before. It was in fact a state of gradually increasing deafness, caused by the constant impact of noise over years. I have not been able to see why, taking one's stand at a particular arbitrary date, the appellant's deafness, then existing, is to be attributed to another factor than boilermaking, namely increasing age. The two factors may, in a sense, he said to have operated concurrently; for, generally speaking, men's hearing tends to deteriorate as they get older. But here a hypothetical deterioration by age was absorbed in continuing impairments by injury. I cannot myself see how the supposed separate components of the man's condition can be separately assessed. (at p227)

3. However, quite apart from my misgivings about the manner of reasoning which the respondent urged us to adopt, I think that on the evidence before him the learned judge of the Commission could come to the end decision he did by the path of reasoning he followed. The only question for us is whether there was evidence which could support his award. In my view there was. I think the appeal should be allowed and the award restored. (at p227)

Appeal allowed with costs. Order of the Supreme Court of New South Wales set aside and in lieu thereof order that the appeal to that Court be dismissed with costs.