Minimization of acoustic echo effects in a microphone boot

A microphone boot system for reducing acoustic echo effect has a first compression structure; a first member of a microphone boot pressing against the first compression structure; second member of the microphone boot pressing against the first member of the microphone boot at an interface; a microphone interposed within a cavity formed by the first member of the microphone boot and the second member of the microphone boot; and a second compression structure juxtaposed against the second member of the microphone boot, such that the first compression structure and the second compression structure acting in concert form an acoustic seal at the interface. A method of reducing acoustic echo effect involves forming a first member of a microphone boot; forming a second member of a microphone boot; interposing a microphone between the first member of the microphone boot and the second member of the microphone boot; and applying a compressive force to the first member of the microphone boot and the second member of the microphone boot so as to form an acoustic seal between the first member of the microphone boot and the second member of the microphone boot at an interface thereinbetween.

BACKGROUND OF THE INVENTION 
The present invention relates to minimizing acoustic echo effects, and more 
particularly to minimizing acoustic echo effects in a microphone boot. 
Even more particularly, the present invention relates to minimizing 
acoustic echo effects in a noise canceling microphone boot for a portable 
radio, such as a portable cellular telephone. 
A major challenge faced by the designer of portable radios, such as 
portable cellular telephones is posed by what is known as "acoustic echo 
effect". This effect occurs when sound emitted from a speaker in a 
portable radio is transmitted to and received by a microphone in the same 
portable radio. For example, when a first person is talking to a second 
person, as the first person's voice is emitted from the speaker in the 
second person's portable radio, it may be picked up by a microphone in the 
second person's portable radio, and consequently, transmitted back to the 
first person. Absent any mechanism for minimizing or preventing "acoustic 
echo effect", the results of this transmission back to the first person is 
that the first person's voice is emitted from the speaker of the first 
person's portable radio, thus "echoing" the first person's own voice 
transmissions. 
Acoustic echo effect is problematic in portable radios, such as portable 
cellular telephones, because of their small size and thus short distance 
between the microphone and speaker, and is particularly problematic in 
digital portable radios, such as digital cellular telephones (e.g., TDMA, 
CDMA, GSN and the like), and even more problematic in satellite 
transceivers, because of the greater delays present in digital and 
satellite environments. Although it is inevitable that some sound emitted 
from a speaker in a portable radio will be picked up by a microphone in 
the same portable radio, acoustic echo effect can be minimized through an 
effective seal around the microphone within such portable radio's housing. 
This seal serves to minimize the amount of sound entering the microphone 
from within the portable radio's housing, which accounts for the majority 
of acoustic echo effect. As a result, most portable radios employ a "boot" 
made from rubber-like material that encloses its microphone and provides a 
seal against plastic housings of the portable radio so as to prevent sound 
from entering the microphone from within the plastic housings. 
Boot designs commonly employed tradeoff performance (i.e., effectivity of 
the seal formed around the microphone) for manufacturablity (i.e., ease 
and speed of assembly), or vice versa. The primary reason for this 
tradeoff is that the microphone typically requires two leads (either in 
the form of wires or a thin plastic flex conductor in which a pair of 
conductors are encompassed or on which such conductors are fused) in order 
to connect the microphone with a circuit board within the plastic 
housings. As a result, there is generally a compromise in the integrity of 
the seal at the point or points from which these two leads emerge from the 
boot. If the point or points at which the leads emerge is sealed well, 
then assembly becomes highly difficult, because the leads must be squeezed 
through tight openings in the microphone's boot. On the other hand, if the 
point or points at which the leads emerge is not sealed well, then 
assembly is simplified, but acoustic echo may be worsened because sound is 
able to enter the microphone through these points. 
The present invention advantageously addresses the above and other needs. 
SUMMARY OF THE INVENTION 
The present invention advantageously addresses the needs above as well as 
other needs by providing an approach to minimizing acoustic echo effects 
in a microphone boot. 
In on embodiment, the invention can be characterized as a microphone boot 
system for reducing acoustic echo effect. The microphone boot system has a 
first compression structure, such as a front housing; a first member of a 
microphone boot pressing against the first compression structure; a second 
member of the microphone boot pressing against the first member of the 
microphone boot at an interface; a microphone interposed within a cavity 
formed by the first member of the microphone boot and the second member of 
the microphone boot, such as in a recess within the first member of the 
microphone boot, and preferably enveloping the microphone within the first 
member of the microphone boot and the second member of the microphone 
boot; and a second compression structure, such as a rear housing pressing 
against the second member of the microphone boot, such that the first 
compression structure and the second compression structure acting in 
concert form an acoustic seal at the interface. Preferably also, the first 
member of the microphone boot and the first compression structure, and the 
second member of the microphone boot and the second compression structure 
form respective acoustic seals thereinbetween as well. 
In a variation of the above embodiment, the microphone boot system has an 
electrical conductor coupled to the microphone. The electrical conductor 
is interposed between the first member of the microphone boot and the 
second member of the microphone boot at the interface between the first 
member of the microphone boot and the second member of the microphone 
boot. The electrical conductor is preferably a flex conductor, and 
preferably is fashioned to form a radial flange around one end of the 
microphone that occupies the interface region, with the first member of 
the microphone boot and the second number of the microphone boot forming 
respective seals on either side of the flange. 
In another embodiment, the present invention can be characterized as a 
method of reducing acoustic echo effect. The method involves forming a 
first member of a microphone boot; forming a second member of a microphone 
boot; interposing a microphone between the first member of the microphone 
boot and the second member of the microphone boot; and applying a 
compressive force to the first member of the microphone boot and the 
second member of the microphone boot so as to form an acoustic seal 
between the first member of the microphone boot and the second member of 
the microphone boot at an interface thereinbetween. Preferably, also, 
respective acoustic seals are formed between a first housing member and 
the first member of the microphone boot, and between the second housing 
member and the second member of the microphone boot when the first housing 
and the second housing are assembled and thereby apply the compressive 
force to the first member of the microphone boot and the second member of 
the microphone boot. 
In a variation, the method also involves interposing a conductor between 
the first member of the microphone boot and the second member of the 
microphone boot at the interface region, and preferably interposing a flex 
conductor that forms a radial flange at one end of the microphone between 
the first member of the microphone boot and the second member of the 
microphone boot and wherein the seal is formed on respective sides of the 
radial flange by the first member of the microphone boot and the second 
member of the microphone boot.

Corresponding reference characters indicate corresponding components 
throughout the several views of the drawings. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following description of the presently contemplated best mode of 
practicing the invention is not to be taken in a Limiting sense, but is 
made merely for the purpose of describing the general principles of the 
invention. The scope of the invention should be determined with reference 
to the claims. 
Referring first to FIG. 1, shown are an upper housing 100, a lower housing 
102, an upper member 104 of a microphone boot, a lower member 106 of a 
microphone boot, a microphone 108, a flex conductor 110, and a ringer 112. 
As can be seen, as represented by dashed lines, the upper and lower 
housings 100, 102 snap together and are secured in place by tabs 114, such 
as is known in the art. In the process of snapping the housings 100, 102 
together, the upper and lower members of the microphone boot 104, 106, 
which are sized to be slightly larger, i.e., from, for example, between 
0.01 and 0.03 inches of interference, than a space between a sound 
directing structure 116 in the upper housing 100 and the sound directing 
structure 118 in the lower housing 102, so as to compress the upper and 
lower members 104, 106 of the microphone boot together upon assembly of 
the upper and lower housings 100, 102. Preferably, Butyl rubber is used to 
make the upper and lower members of the microphone boot 104, 106, however, 
numerous materials with acoustic insulating properties can be used within 
the scope of the present embodiment. The sound directing structures 104, 
106 of the upper and lower housings lead to respective sound ports 120, 
122 through which sound enters the upper and lower housings 100, 102. From 
the sound directing structures 120, 122, the sound entering the upper and 
lower housings 100, 102 is directed respectively, through the upper and 
lower members 104, 106 of the microphone boot to the microphone 108. A 
radial flange 115 formed from the flex conductor 110 is adjacent to one 
end of the microphone 108 and the microphone 108 is compressed between and 
held within the upper and lower members 104, 106 of the microphone boot, 
which form respective seals against respective sides of the radial flange 
formed by the flex conductor 110 at one end of the microphone 108 such 
that sound is not able to or is highly impeded from entering the 
microphone boot other than through the sound ports 120, 122 in the upper 
and lower housings 100, 102. 
The compression applied to the upper and lower members 104, 106 of the 
microphone boot is sufficient to form the seals against the respective 
sides of the radial flange formed 115 by the flex conductor 110 adjacent 
to one end of the microphone 108 at the interface of the upper member 104 
of the microphone boot and the lower member 106 of the microphone boot. 
The radial flange 115 occupies the interface region between the upper 
member of the microphone boot 104 and the lower member of the microphone 
boot 106. The flex conductor 110 also electrically couples the microphone 
108 to circuits (not shown) within the housing 100, 102, such as portable 
radio circuits. The compression applied to the upper and lower members 
104, 106 of the microphone boot is as a result of the upper member of the 
microphone boot 104 and the lower member of the microphone boot 106 being 
slightly larger than the space between the upper sound directing structure 
116 and the lower sound directing structure, such as an interface of from 
between about 0.01 inches and 0.03 inches. 
Also shown is a ringer 112, which in the present embodiment also supported 
by the microphone boot between an upper ringer supporting structure 124 of 
the upper member 104 of the microphone boot, and a lower ringer supporting 
structure 126 of the lower member 106 of the microphone boot. In the 
embodiment shown, the flex conductor 110 from the microphone 108 passes 
between the upper ringer supporting structure 124 and the ringer 112, 
which serves to hold the flex conductor 110 securely in place, and prevent 
stresses on the flex conductor 110 from jeopardizing the integrity of the 
seal around the microphone 108, as formed by the upper and lower members 
104, 106 of the microphone boot. 
The lower ringer supporting structure 126 includes an opening 130, which 
upon assembly of the upper and lower members 104, 106 of the microphone 
boot and the upper and lower housings 100, 102, is adjacent to a ringer 
port 132 through which sound emanating from the ringer 112 exits the lower 
housing 102, so as to notify a user that, for example, an incoming call is 
being received. 
Wires 136 connecting the ringer 112 to circuits within the upper and lower 
housing 102, 104 pass through and make electrical contact with the flex 
conductor 110 and pass into clearance holes 134, 136 in the upper ringer 
supporting structure 124. The wires 136 are connected to, e.g., soldered 
to, respective conductors within the flex conductor by piercing through 
the flex conductor 110 at such conductors. 
Referring next to FIG. 2, shown is the upper member 104 of the microphone 
boot, including the upper ringer supporting structure 124. Also shown is a 
hole 200 into which the microphone is placed during assembly, the holes 
134 through which the wires of the ringer pass, and a notch 202 through 
which the flex conductor passes. 
Referring next to FIG. 3, shown is the upper member 104 of the microphone 
boot, including the upper ringer supporting structure 124, the opening 200 
into which the microphone is placed, and an opening 300 that directs sound 
from the upper sound port into the microphone, as channeled by the upper 
sound directing structure. 
Referring next to FIG. 4, shown is the lower member 106 of the microphone 
boot, including the lower ringer supporting structure 126, as well as an 
opening 400 into which sound entering the lower sound port is channeled 
into the microphone by the lower sound directing structure. 
Referring next to FIG. 5, shown are the lower member 106 of the microphone 
boot, including the lower ringer supporting structure 126, the opening 130 
in the lower ringer supporting structure, and the opening 400 in the lower 
member of the microphone boot through which sound from the lower sound 
port is directed by the sound directing structure. 
Referring next to FIG. 6, shown are the upper and lower members 104, 106 of 
the microphone boot, including the opening 200 into which the microphone 
is inserted, the opening 300 in the lower member of the microphone boot 
into which sound enters from the lower sound port, and the opening 400 in 
the lower member of the microphone boot through which sound enters from 
the upper microphone port. Also shown are the flex conductor 110, the 
microphone 108, the ringer 112, the upper and lower ringer supporting 
structures 124, 126, the opening 130 in the lower ringer supporting 
structure through which sound from the ringer 112 exits into and through 
the ringer port, and one of the holes 134 in the upper ringer supporting 
structure 124 into which one of the wires 136 connected to the ringer 112 
passes. 
In operation, a seal 600 is formed around the microphone at the 
intersection (or interface) of the upper member 104 of the microphone 
boot, and the lower member 106 of microphone boot, which form respective 
seals against respective sides of the radial flange 115 formed by the flex 
conductor at one end of the microphone 108 so as to prevent or impede 
sound emanating from within the upper and lower housings from entering the 
microphone 108. Such sound can, for example, come from a speaker located 
within the upper and lower housings and is the predominant source of the 
acoustic echo effect. 
Advantageously, no tedious threading of microphone wires through tiny holes 
is needed to assemble the microphone boot, because the flex conductor 110 
is an integral part of the seal 600 at the interface and passes out toward 
the ringer 112, without any breaking of the seals such as would be 
necessary to provide passage for wires out of the microphone boot. This 
advantageous feature is as a result of the fact that, in accordance with 
the present embodiment, the seals are formed by the juxtaposition of 
relatively flat surfaces of the upper member of the microphone boot 106 
and one side of the flex conductor 110 and the juxtaposition of relatively 
flat surfaces of the lower member of the microphone boot 104 and another 
side of the flex conductor 110, thus sandwiching the flex conductor 110 
between the upper and lower members 104, 106 of the microphone boot. 
Further advantageously, the seal 600 is formed when the upper and loser 
housings are snapped together as a result of compressive forces imposed on 
the microphone boot by the upper and lower sound directing structures and 
the upper and lower housings. Advantageously, assembly of the upper and 
lower housings in this way is not only an already necessary step, but also 
a quick and simple step as compared to the tedium of threading wires 
through holes. 
While the invention herein disclosed has been described by means of 
specific embodiments and applications thereof, numerous modifications and 
variations could be made thereto by those skilled in the art without 
departing from the scope of the invention set forth in the claims.