Patent Application
20170272868
This disclosure relates to acoustic devices and, more specifically, to acoustic devices including drivers having filters for controlling the performance of the drivers.
Various types of acoustic devices have been used through the years. These devices may include a receiver or driver having a diaphragm, coil, bobbin, stack, and other components within a housing. Some acoustic devices include multiple drivers that produce different frequency sounds for a listener. Examples of such acoustic devices include hearing aids, earphones, smartphones, laptop computers, and personal entertainment devices.
Some prior acoustic devices have an ear bud or similar structure that houses a low-frequency (LF) driver and a high-frequency (HF) driver, wherein the LF driver produces low frequency sound and the HF driver produces high frequency sound. However, the LF driver and the HF driver may produce sounds that have resonant peaks at the same frequency (approximately 5-7 kHz) and these peaks tend to add together. The summation of sounds can yield unpredictable and degraded sound quality.
To address this unwanted sound distortion, in one prior approach an acoustic resistance (e.g., a screen) is used as a low-pass filter for a LF driver and a capacitor, connected in series with a HF driver, acts as a high-pass filter for the HF driver. These filters may attenuate resonance of the LF driver, remove undesired bass response from the HF driver, and produce better quality sound.
In this prior approach, the LF driver and the HF driver are conjoined in such a manner as to form a common front volume and have a common outlet tube. Sounds produced by the LF driver and the HF driver interact within the acoustic device, travel through the outlet tube, exit the acoustic device, and enter a user's ear canal.
One issue with this prior approach is that the shared front volume of the LF driver and the HF driver involves a complex geometry. Tuning the performance of the LF driver for a particular acoustic device may require substantial redesign of the conjoined LF and HF drivers. Another issue is that changes to the front volume of the LF driver may affect the performance of the HF driver and further complicates engineering and manufacture.
For a more complete understanding of the disclosure, reference should be made to the following detailed description and accompanying drawings wherein:
Persons having ordinary skill in the art will appreciate that elements in the figures are illustrated for simplicity and clarity. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence although such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning in the art except where specific meanings have otherwise been set forth herein.
In accordance with one aspect of the present disclosure, a low frequency driver is provided having a diaphragm operable to produce sound, a front volume, and an outlet that receives sound from the front volume and directs sound out from the low frequency driver. The low frequency driver further includes a low-pass filter chamber in communication with the front volume. In this manner, the low-pass filter chamber effectively enlarges the front volume and provides improved roll-off of the response of the low-frequency driver at higher frequencies. Further, the low-pass filter chamber permits the response of the low frequency driver to be acoustically tuned for a particular application in a cost effective and straightforward manner.
In one form, the low frequency driver has a housing containing the movable diaphragm, the front volume, and the low-pass filter chamber. The housing comprises a body including the front volume and the diaphragm and further comprises a cap connected to the body. The body and cap define at least a portion of the low-pass filter chamber therebetween. The response of the low frequency driver may be tailored for a particular application by selecting a cap having a particular geometry, such as an interior volume, from a plurality of caps having different interior volumes. For example, a cap having a larger interior volume may be selected and secured to a body of a low frequency driver for an application where greater dampening of a second resonant frequency of the low frequency driver is desired. Conversely, a cap having a smaller interior volume may be selected and secured to the body of the low frequency driver for an application where less dampening of the second resonant frequency is required.
Referring now to
The in-the-ear component 12 includes one or more drivers, such as a LF driver 14 and a HF driver 16. Typically, LF drivers produce sound in the range of approximately 20 Hz to approximately 8 kHz frequency and HF drivers produce sound in the range of approximately 4 kHz to approximately 20 kHz frequency range, and thus have a typical overlap in response. The in-the-ear component 12 directs the sound toward a user's eardrum through a tube 15 extending from the LF driver 14 and a tube 17 extending from the HF driver 16.
With reference to
With continued reference to
The low-pass filter chamber 47 may be formed integrally as a part of the housing 50. In another form, the housing 50 includes a body 61 and a cover member, such as cap 55, connected to the housing 50. The body 61 and cap 55 together define at least a portion of the low-pass filter chamber 47. The body 61 has a wall 53 separating the front volume 52 and the low-pass filter chamber 47. The cap 55 has one or more sidewalls 55A depending from the body 61 and a cover wall 55B extending transversely to the sidewalls 55A. In one form, the body 61 and cap 55 together define the entirety of low-pass filter chamber 47.
The LF driver 14 includes a port 48 permitting the passage of air between the front volume 52 and the low-pass filter chamber 47. The port 48 may have a number of forms, such as a tube or one or more openings. In
In one form, the LF driver 14 is not acoustically linked to the HF driver 16. As used herein, the term “not acoustically linked” is intended to refer to the response of the LF driver 14 not being controlled by or significantly impacted by the response of the HF driver 16.
With reference to
In
The response of the HF driver 16 represented by curve 69 is in the range of approximately 4 kHz to approximately 20 kHz, and the response of the LF drivers represented by the curves 67, 70 are in the range of approximately 20 Hz to approximately 8 kHz. The HF driver 16, the LF driver without the low-pass filter chamber 47, and the LF driver 14 with the low-pass filter chamber 47 generate main mechanical resonance peaks 62, 63, 65 along the curves 69, 67, 70. The HF driver 16 and the LF driver without the low-pass filter chamber 47 also exhibit second acoustic peaks 64, 68 along the curves 69, 67. As shown in
With reference to
The geometry of the low-pass filter chamber 47 may be selected to provide a desired response of the LF driver 14. For example, the low-pass filter chamber 47 has a height 57 (see
The low-pass filter chamber 47 may be formed in a number of ways. For example, the body 61 may initially be provided with the body 61 including the back volume 44, diaphragm 54, front volume 58, and tube portion 46. Next, an opening is formed in the wall 53 to form the port 48, such as by stamping. The cap 55 is positioned over the wall 53 so that the cap 55 covers the port 48. The cap 55 may then be secured to the body 61 such as by welding, using an adhesive, using one or more fasteners, or other approaches.
The cap 55 may be made of plastic, metallic, or other materials. Likewise, the body 61 may be made of plastic, metallic (such as stainless steel, mu-metal, and aluminum), or other materials and be similar to or different from the materials of the cap 55. The diaphragm 54 may be made of a metallic material, such as stainless steel or aluminum.
With reference to
Preferred embodiments are described herein, including the best mode known to the inventor(s) for carrying out the disclosure. It should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the disclosure.
