WO1991007153A1

WO1991007153A1 - A hearing protector set

Info

Publication number: WO1991007153A1
Application number: PCT/DK1990/000297
Authority: WO
Inventors: Per Rubak
Original assignee: Panacoustics A/S
Priority date: 1989-11-17
Filing date: 1990-11-16
Publication date: 1991-05-30
Also published as: AU6731490A; DK576889D0; EP0502017A1

Abstract

Hearing protectors of the cup shaped ear covering type should preferably be provided with a sound transfer system which is an acoustic channel (14) or an electroacoustical coupling comprising an exterior microphone and an interior loudspeaker, all adjusted such that the user can hear sound and noise at a moderate intensity level with preference for speech frequencies. An associated problem, however, is that it is impossible to determine the direction to a specific sound source, and according to the invention this problem is counteracted by shaping the outer sides (6) of the cups (2) as rough imitations of the human pinna, these outsides (6) being arranged so as to converge forwardly and having various depressions (8, 10), of which a concha imitating depression (8) is connected with the inlet (14, 16) of the sound transfer system. Also hearing protectors of the supra aural type can be designed in this manner.

Description

A hearing protector set

The present invention relates to a hearing protec¬ tor comprising a pair of sound insulating cover members to be placed on or over the ears of the user. This type of hearing protector is preferred for ear plugs, because the cup protectors are easy to mount and dismount and easy to 'lift briefly when required. They can be made with almost any degree of damping effect, and when pro¬ perly supported they will not interfere with the outer ear and thus be reasonably comfortable to wear.

Hearing protectors should not exhibit any absolute sound insulation, but merely cut the top of the noise. It is already known that with the use of various acou¬ stic membranes and other features it is possible to adapt the protectors such that the frequency range of intelligible human speech may pass without much attenua¬ tion, while noise frequencies outside this range may be damped considerably more. A similar effect is achievable with the use of an electroacoustic transfer system, i.e. based on the use of an exterior microphone and an ear¬ phone speaker in each of the cups, whereby almost any desired transfer characteristic can be provided with the use of suitable electric filter means.

Thus, the damping characteristic of the protectors can be almost optimized, but it is a common experience that the protectors exhibit one clear disadvantage, viz. that it is very difficult or even impossible for the user to localize the direction to a distinct source of sound or noise. This can be generally rather inconve¬ nient and even dangerous in special cases. It has been found that the same difficulty applies to 'stereo pro¬ tectors', i.e. protector sets with individual micro¬ phones on the cups, and relevant attempts of overcoming the problem by sophisticating the applied electrical filter means have not succeeded so far and are in fact not liable to succeed at all. .

It is the purpose of this invention to provide a hearing protector which will allow the user to determine the direction to a specific source of noise or sound, without the attainment of this extra advantage implying undesirable adverse effects in other respects.

The invention is based on a mere scientific know¬ ledge of the fact that the shape of the natural human ear lobe or pinna is of importance for the ability to determine the sound direction, when the received signals are processed in the human brain. In the patent litera¬ ture this has been confirmed in US-A-3,513,937, which discloses an acoustic transducer to be held over the ear and taking an almost grotesque shape as a human pinna enlarged five or six times; it is claimed that this artificial ear is capable of amplifying sound, this not exactly being the purpose of the invention, but it is clearly confirmed that with the use of such an amplifier the ability to determine the sound direction will be maintained.

Quite another approach in the field of human hear¬ ing has been entered by the creation of artificial heads with simplified pinnae and with microphones fitted in the associated artificial auditory canals. Such dummies may serve various useful purposes, but they can have no bearing on perception processes, in which the brain plays an important roll, such as in the present connec¬ tion. These known dummies, therefore, have been of no use or relevance for an investigation of how a human hearer determines the direction of incidence of a sound signal.

Based on numerous experiments it has now been found that the ability of the person wearing the hearing pro¬ tectors to ascertain the direction of an in-falling sound or noise can be reestablished when the outer sur- face of the single cover members is shaped so as to imitate the main shape of the natural pinna, without being much larger than the natural pinna. As the cover members of the circum aural type are bound to be larger than the pinna, because they surround the pinna, the outer imitated pinna may well be larger than the natural pinna, but in no way more than twice the size thereof, as the protector would otherwise be found absolutely unusable in practice.

It is an important result of the invention, there¬ fore, that it is possible to provide a hearing protector having a normal 'small' size and yet having the ability to offer to the user the possibility of determining the direction of the received sound or noise as otherwise damped by the damping function of the respective protec¬ tor members or cups.

It has been found that for this purpose it is suf¬ ficient to imitate the pinna only very roughly, such that the size and appearance of the cover members will not be radically changed. The outsides of the cups will not be smoothly rounded as for conventional ear cups, but still the cups can appear with a compact shape. There are two main conditions for the pinna imitation, viz. that the outer cup sides be generally planar and oriented substantially vertically and mutually forwardly converging and that in both of these outsides there is provided a depression schematically imitating the larger depression, the concha, of the pinna and, optionally a depression extending upwardly therefrom, imitating the pinna area just inside the outer rim portion, the tuber- culum auriculare, of the pinna. The imitations of the natural depressions may be designed with very simple geometrical shapes, such that the look of the outsides of the ear cups will in no way be ear-like.

For measuring purposes there has already been de¬ veloped several artificial pinnae with simplified con- figurations, and the invention is not limited to any particular design of the outer cup surfaces, when only they comprise a sufficient ear feature imitation to condition the desired result of the ear cups giving rise to a direction perception of received sound or noise.

Once the outsides of the protector cups are shaped in this manner the desired result will be achieved when the sound or noise is transmitted to the ears either acoustically, through a suitably damped transfer channel from the bottom of the concha imitation to the natural ear canal of the user, or electroacoustically, by means of microphones located at the bottom of the said concha imitations and connected to internal loudspeakers through suitable electrical filter means. In both cases a desirable attenuation effect and transfer function will be achievable, and still the user or at least the vast majority of users will be able to locate the direc¬ tion of the received sound or noise.

In the prior art it has been customary to focus on a transfer of the speech frequency range between approx¬ imately 300 Hz and 3000 Hz, with strong attenuation of frequencies above this range. For the determination of the sound direction, however, it has been found impor¬ tant to include also the range from 3000 Hz up to ap¬ proximately 10.000 Hz. The use of this widened transfer frequency range gives rise to a very advantageous addi¬ tional effect, viz. that it becomes possible for the user to keep various 'process sounds' under surveil¬ lance. Traditional hearing protectors attenuate the higher frequencies far too much to enable such an audi¬ tive surveillance of most machines and working pro¬ cesses, preferably, for ensuring a good sound localiza¬ tion the reproduced sound spectrum should not be too distorted, and in fact it is seldom imperative to atten¬ uate the high frequencies heavily.

It should be noted that the principle of the inven- tion is also fully applicable to hearing protectors of the supra aural type, i.e. where the cover members are rested directly against the pinnae of the user, normally through a soft foam layer.

In the following the invention is described in more detail with reference to the drawing, in which:

Fig. 1 is a perspective view of a hearing protector set according to the invention, and

Fig. 2 is a sectional view of one of the ear cups thereof, seen along the line II-II in Fig. 1.

The protector set shown in Fig. 1 comprises a pair of opposed ear cups 2 having generally parallel, inter¬ facing inner sides 4 shaped with annular configurations so as to fit over the ears of the user. The outer sides 6 of the ear cups 2 are generally planar and are pro¬ nounced forwardly converging, towards the left.

In each of the outsides 6 there is provided a de¬ pression, viz. a relatively deep depression 8 outside the natural ear canal of the user and a shallower de¬ pression 10 extending upwardly from the rear end of this depression, whereby the rearmost portion 12 of the sur¬ face 6 will represent the tuberculum auriculare of the natural ear. At the bottom portion of the lower depres¬ sion 8 is provided a transmission channel 14 leading to the interior of the protector cup, and in this channel may be provided either an acoustical membrane system or a microphone 1.6 connected with an internal loudspeaker (not shown) . Generally, of course, the cups are made with the desired sound insulating properties.

The artificial pinnae as represented by the out¬ sides 6 of the cups may have other detailed designs, but it is deemed important that the outsides, whether planar or more or less curved, are configured so as to be rear- wardly outstanding or forwardly converging, forming an angle of 10-20° with the median plane of the head, pre¬ ferably 15-18°. They may even be slightly inclined up- wardly and outwardly.

For the protector set in practice it is of course important that the sound transfer to the ear is well controlled according to the requirements, and the cups can be highly developed in this respect, with the use of various acoustical membranes and/or electronic filter means, but the basic effect of the invention, viz. the possibility of the user to localize the direction of directional sound or noise, does not seem, itself, to be particularly dependent of the transfer system being more or less sophisticated. For that reason it is deemed needless to disclose the transfer system in more detail in the present connection. Fully usable systems are already known in the art from the conventional hearing protectors.

Claims

C L A I M S :

1. A hearing protector set of the type comprising a pair of sound insulating cover members to be placed on or over the ears of the user, each of said cover members being generally sound insulating, but having an acoustic or electroacoustic sound transfer system enabling the user to hear sound and noise at a moderate intensity level at least in the speech frequency range, charac¬ terized in that the outer side (6) of each cover member (2) is designed as a schematic imitation of the outside of the human pinna, sized less than the double height and width thereof and having an outer surface generally converging forwardly towards the vertical longitudinal . iddle plane of the head, said imitation comprising a lower depression (8) connected with an inlet of said sound transfer system (14, 16) and preferably a depres¬ sion (10) extending upwardly from the lower depression.

2. A protector set according to claim 1, in which the upwardly extending depression (10) is a relatively shallow groove projecting substantially upright from the rear upper area of the lower depression.