Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND SYSTEM FOR CONTROLLING A MAXIMUM SIGNAL
LEVEL OUTPUT TO HEADPHONES COUPLED TO A WIRELESS DEVICE
FIELD OF THE APPLICATION
[0001]This application relates to the field of wireless
devices, and more specifically, to a method and system for
controlling a maximum signal level output to headphones
coupled to a wireless device.
BACKGROUND
[0002]Current wireless mobile communication devices include
microprocessors, memory, soundcards, speakers, headphones, and
run one or more software applications in addition to providing
for voice communications. Examples of software applications
used in these wireless devices include micro-browsers, address
books, email clients, instant messaging ("IM") clients, and
wavetable instruments. Additionally, wireless devices have
access to a plurality of services via the Internet. A wireless
device may, for example, be used to browse web sites on the
Internet, to transmit and receive graphics, and to execute
streaming audio and/or video applications. Such wireless
devices may operate on a cellular network, on a wireless local
area network ("WLAN"), or on both of these types of networks.
[0003]One problem with current wireless devices pertains to the
adjustment of maximum output sound pressure levels for
headphones coupled to such devices. Headphones are typically
used to listen to voice calls, radio programs, audio programs
(e.g., music), etc., stored on or accessed by the wireless
device. In particular, the maximum output sound pressure level
for headphones for wireless devices and handheld products is
legally constrained in several jurisdictions in order to
protect users from hearing loss. For example, European
Standard EN 50332-1:2000, dated March 2000 and entitled "Sound
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System Equipment: Headphones And Earphones Associated With
Portable Audio Equipment - Maximum Sound Pressure Level
Measurement Methodology And Limit Considerations - Part 1:
General Method For 'One Package Equipment", restricts maximum
sound pressure level at the headphones (i.e., for headphones
provided with the portable audio equipment and from the same
manufacturer) to 100 dB. In addition, European Standard EN 50332-
2:2003, dated October 2003 and entitled "Sound System Equipment:
Headphones And Earphones Associated With Portable Audio Equipment
- Maximum Sound Pressure Level Measurement Methodology And Limit
Considerations - Part 2: Matching Of Sets With Headphones If
Either Or Both Are Offered Separately", restricts maximum sound
pressure level at the headphones (i.e., for headphones provided
separately from the portable audio equipment by a different
manufacturer) to 94 dB. Measurement of maximum sound pressure
levels according to these standards is specified with respect to
headphones having an impedance of 32 Ohms. One problem relating
to such standards is that in order to set the output signal level
(e.g., in mV RMS) appropriately at the output jack of the
wireless device in order to meet the maximum sound pressure level
specified, the impedance of the headphones must be known. This is
especially problematic if the headphones are not provided by the
manufacturer as a package with the wireless device.
[0004] A need therefore exists for an improved method and system
for controlling a maximum signal level output to headphones
coupled to a wireless device. Accordingly, a solution that
addresses, at least in part, the above and other shortcomings is
desired.
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BRIEF DESCRIPTION OF THE DRAWINGS
N005,1Features and advantages of the embodiments of the present
application will become apparent from the following detailed
description, taken in combination with the appended drawings,
in which:
[0006]FIG. 1 is a front view illustrating a wireless device
coupled to headphones and adapted for implementing an
embodiment of the application;
[0007]FIG. 2 is a block diagram illustrating the wireless
device of FIG. 1 and a wireless network adapted for
implementing an embodiment of the application;
[0008]FIG. 3 is a block diagram illustrating a memory of the
wireless device of FIGS. 1 and 2;
[0009]FIG. 4 is a block diagram illustrating a headphones
subsystem in accordance with an embodiment of the application;
[0010] FIG. 5 is a block diagram illustrating an alternate
headphones subsystem in accordance with an embodiment of the
application; and,
[0011] FIG. 6 is a flow chart illustrating operations of modules
within the memory of a wireless device for controlling maximum
signal level output to headphones of the wireless device, in
accordance with an embodiment of the application.
[0012] It will be noted that throughout the appended drawings,
like features are identified by like reference numerals.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0013] In the following description, details are set forth to
provide an understanding of the application. In some
instances, certain software, circuits, structures and
techniques have not been described or shown in detail in order
not to obscure the application. Embodiments of the present
application may be implemented in any computer programming
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language provided that the operating system of the wireless
device or data processing system provides the facilities that
may support the requirements of the application. Any
limitations presented would be a result of a particular type
of operating system or computer programming language and would
not be a limitation of the present application. Embodiments of
the preset application may also be implemented in hardware or
in a combination of hardware and software.
[0014]According to one embodiment of the application, there is
provided a method for controlling a maximum signal level
output to headphones of a wireless device. The method
includes: determining an impedance of the headphones;
determining a carrier specific maximum signal level for
headphones having the impedance; and, adjusting an audio
amplifier of the wireless device coupled to the headphones to
restrict the maximum signal level output to the headphones to
the carrier specific maximum signal level.
[0015]FIG. 1 is a front view illustrating a wireless device 100
coupled to headphones 105 (a.k.a., headphone set, headphone,
headset, earphone, earphones, etc.) and adapted for
implementing an embodiment of the application. The wireless
device 100 includes a casing 150, a display screen 122, a
graphical user interface ("GUI") 180 displayed on the display
screen 122, a keyboard (or keypad) 132, a trackball (or
thumbwheel) 110, various select buttons 120, various
inputs/outputs (e.g., power connector jack, data interface
ports, etc.) 160, and a headphones jack 106. Internally, the
wireless device 100 includes one or more circuit boards (not
shown), a CPU 138, memory 124, 126, 200, a battery 156, an
antenna (not shown), etc., which are operatively coupled to
the various inputs/outputs 160, the keyboard 132, the display
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screen 122, the headphones jack 106, etc., as will be
described below.
[0016] The headphones 105 are coupled to the wireless device 100
by a headphones cable or lead 107 which is inserted into the
5 headphones jack 106. The headphones 105 include a speaker
assembly which is inserted into or placed over a user's ear.
According to one embodiment, the headphones 105 include two
speaker assemblies, one for each of the user's ears. Each
speaker assembly includes a speaker having an impedance
(referred to as the impedance of the headphones in the
following). The headphones 105, headphones jack 106, and
headphones cable 107 may be configured for stereo and/or mono
operation. When the headphones cable 107 is inserted into the
headphones jack 106, audio output signals may be switched from
the internal speaker 134 (see FIG. 2) to the headphones 105.
Control of audio signal level (e.g., in mV RMS) output to the
headphones 105 is performed by a headphones subsystem 400 as
described below. According to one embodiment, the headphones
jack 106 is a 3.5 mm headset jack adapted to support both a
stereo headphones output and a mono microphone input.
[0017] FIG. 2 is a block diagram illustrating the wireless
device 100 of FIG. 1 and a wireless network 220 adapted for
implementing an embodiment of the application. The wireless
network 220 may include antenna, base stations, access points,
transceivers, supporting radio equipment, etc., as known to
those of ordinary skill in the art, for supporting wireless
communications between the wireless device 100 and other
devices (not shown).
[0018] The wireless device 100 may be a two-way communication
device having at least voice and advanced data communication
capabilities, including the capability to communicate with
other devices. Depending on the functionality provided by the
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device 100, it may be referred to as a data messaging device,
a two-way pager, a cellular telephone with data messaging
capabilities, a wireless Internet appliance, a data
communication device (with or without telephony capabilities),
a Wi-Fi device, a WLAN device, a dual-mode (i.e., Wi-Fi and
cellular) device, or a portable audio device.
[0019]The wireless device 100 has a communication subsystem
111, which includes a RF receiver, a RF transmitter, and
associated components. As will be apparent to those skilled in
the field of communications, the particular design of the
communication subsystem 111 depends on the communication
network 220 in which the device 100 is intended to operate.
[0020]The device 100 may be capable of cellular network access
and hence the device 100 may have a subscriber identity module
(or "SIM" card) 162 for inserting into a SIM interface ("IF")
164 in order to operate on the cellular network (e.g., a
global system for mobile communication ("GSM") network).
[0021]The device 100 may be a battery-powered device and so it
may also include a battery IF 154 for receiving one or more
rechargeable batteries 156. The battery (or batteries) 156
provides electrical power to most if not all electrical
circuitry in the device 100, and the battery IF 154 provides
for a mechanical and electrical connection for it.
[0022] The wireless device 100 includes a microprocessor 138,
also called a processor, which controls overall operation of
the device 100. The microprocessor 138 interacts with device
subsystems such as the display 122, a flash memory 124 or
other persistent store, a random access memory ("RAM") 126,
auxiliary input/output ("I/O") subsystems 128, a serial port
(e.g., a universal serial bus ("USB") port) 131, the keyboard
132, the trackball or thumbwheel 110, the headphones 105, an
internal speaker 134, a microphone 136, a short-range
communications subsystem 141, and other device subsystems 142.
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The microprocessor 138, in addition to performing operating
system functions, preferably enables execution of software
applications on the device 100.
[0023]FIG. 3 is a block diagram illustrating a memory 200 of
the wireless device 100 of FIGS. 1 and 2. The microprocessor
138 is coupled to the memory 200. The memory 200 has various
hardware and software components for storing information
(e.g., instructions, data, database tables, test parameters,
etc.) for enabling operation of the device 100 and may include
flash memory 124, RAM 126, ROM (not shown), disk drives (not
shown), etc. In general, the memory 200 may include a variety
of storage devices typically arranged in a hierarchy of
storage as understood to those skilled in the art.
[0024]Operating system ("0/S") software modules 202 used by the
microprocessor 138 may be stored in a persistent store such as
the flash memory 124, which may alternatively be a read-only
memory ("ROM") or similar storage element (not shown). Those
skilled in the art will appreciate that the operating system,
specific device applications, or parts thereof, may be
temporarily loaded into a volatile store such as RAM 126.
[0025]To provide a user-friendly environment to control the
operation of the device 100, operating system ("0/S") software
modules 202 resident on the device 100 provide a basic set of
operations for supporting various applications typically
operable through the GUI 180 and supporting GUI software
modules 204. For example, the 0/S 202 provides basic
input/output system features to obtain input from the
auxiliary I/O 128, the keyboard 132, the trackball or
thumbwheel 110, and the like, and for facilitating output to
the user through the display 122, the speaker 134, the
headphones 105, etc. According to one embodiment, the wireless
device 100 is provided with hardware and/or software modules
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206 for facilitating and implementing the method of the
application as will be described below.
[0026]A user may interact with the wireless device 100 and its
various software modules 202, 204, 206, using the GUI 180.
GUIs are supported by common operating systems and provide a
display format which enables a user to choose commands,
execute application programs, manage computer files, and
perform other functions by selecting pictorial representations
known as icons, or items from a menu through use of an input
or pointing device such as a trackball or thumbwheel 110 and
keyboard 132. The GUI 180 may include a cursor 190, various
selectable objects and icons 191, and various windows 192.
[0027]Thus, the wireless device 100 includes computer
executable programmed instructions for directing the device
100 to implement the embodiments of the present application.
The programmed instructions may be embodied in one or more
hardware or software modules 206 which may be resident in the
memory 200 of the wireless device 100. Alternatively, the
programmed instructions may be embodied on a computer readable
medium (such as a CD disk or floppy disk) which may be used
for transporting the programmed instructions to the memory of
the wireless device 100. Alternatively, the programmed
instructions may be embedded in a computer-readable signal or
signal-bearing medium that may be uploaded to a network 220 by
a vendor or supplier of the programmed instructions, and this
signal or signal-bearing medium may be downloaded through an
interface 111, 131, 141 to the wireless device 100 from the
network 220 by end users or potential buyers.
[0028]FIG. 4 is a block diagram illustrating a headphones
subsystem 400 in accordance with an embodiment of the
application. Components of the headphones subsystem 400 are
generally contained in the wireless device 100 and are used to
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determine the impedance of the headphones 105 in order to
adjust the maximum signal level (e.g., in mV RMS) output to
the headphones 105 (and hence the maximum sound pressure level
output by the headphones 105).
[0029]According to one embodiment, the headphones system 400
includes a signal generator 410, a digital to analog converter
("DAC") 440, and an audio amplifier 430 for generating an
inaudible high frequency signal (e.g., 25 kHz). The signal
generator 410, DAC 440, and audio amplifier 430 are controlled
by the microprocessor 138. The audio amplifier 430 is coupled
to the headphones 105 through a series resistor R. The series
resistor R may have a low value (e.g., 5 Ohms). A voltage V
produced across the resistor R when the high frequency signal
is applied to the resistor R and headphones 105 is indicative
of the impedance Z of the headphones 105. The signal may be
applied to the resistor R and headphones 105 whenever the
headphones 105 are connected to the headphones jack 106 via
the headphones cable 107. The voltage V is amplified by a
microphone pre-amplifier 450 which is coupled to an analog to
digital converter ("ADC") 420. The ADC 420 monitors the
voltage V and provides a digital signal indicative of the
voltage V and hence the impedance Z of the headphones 105 to
the microprocessor 138. The ADC 420 may also be used by the
microphone 136 of the wireless device 100 in order to reduce
component count. The microprocessor 138 receives the digital
signal from the ADC 420 and determines the impedance Z of the
headphones 105 from it (e.g., by voltage divider principles,
etc.). The microprocessor 138 may do this by accessing a table
that stores voltage values (or digital signal values) and
corresponding headphones impedance values.
(0030]Having determined the impedance Z for the headphones 105,
the microprocessor 138 controls the audio amplifier 430 to
restrict the maximum signal level (e.g., in mV RMS) output to
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the headphones 105. In this way, the sound pressure level
output by the headphones 105 may be restricted to a maximum
sound pressure level for the determined impedance Z. The
microprocessor 138 may do this by accessing a table (e.g.,
5 included in or associated with modules 206) that stores
headphones impedance values, corresponding maximum signal
level values for the audio amplifier 430, and/or corresponding
maximum sound pressure values for the headphones 105. For
example, for a headphones impedance value of approximately 32
10 Ohms, the table 406 may indicate that the maximum sound
pressure level for the headphones 105 is 100 dB.
[0031J According to one embodiment, if a headphone impedance
value corresponding to the determined headphone impedance Z is
not listed in the table 406, no maximum signal level for the
audio amplifier 430 and no maximum sound pressure level for
the headphones 105 is prescribed and hence the maximum signal
level of the audio amplifier 430 and the maximum sound
pressure level for the headphones 105 are not restricted for
that value of determined headphones impedance Z.
[0032]Now, the maximum signal level (e.g., in mV RMS) and/or
the maximum sound pressure level (e.g., in dB) for a given
headphones impedance may be set by government regulation which
may change depending on the carrier or the location in which
the wireless device 100 is operating or is sold. As is known
to those skilled in the art, the wireless device 100 has means
for determining its carrier and/or location and hence the
government regulations that may apply to set maximum signal
levels and/or maximum sound pressure levels. Thus, according
to one embodiment, the microprocessor 138 receives a signal
indicative of the carrier and/or location of the wireless
device 100 and determines whether a maximum signal level value
and/or a maximum sound pressure level value has been
prescribed for the carrier and/or location and for the
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determined headphones impedance Z. The microprocessor 138 may
do this by accessing a table 406 that stores wireless device
location, corresponding headphones impedance values,
corresponding carrier (or location) specific maximum signal
level values (if any) for the audio amplifier 430, and/or
corresponding carrier (or location) specific maximum sound
pressure level values (if any) for the headphones 105. For
example, the table may indicate that if the wireless device
100 is associated with a carrier based in Great Britain and if
the headphones impedance is 32 Ohms (i.e., +/- 20%), then the
maximum sound pressure level should be restricted to 100 dB
(i.e., if the headphones 105 and wireless device 100 are sold
as a package). As another example, the table 406 may indicate
that if the wireless device 100 is associated with a carrier
based in Great Britain and if the headphones impedance is 32
Ohms (i.e., +/- 20%), then the maximum sound pressure level
should be restricted to 94 dB (i.e., if the headphones 105 and
wireless device 100 are not sold as a package).
[0033]Similarly, the maximum signal level (e.g., in mV RMS)
and/or the maximum sound pressure level (e.g., in dB) may be
set by government regulation which may change depending on the
carrier or the location in which the wireless device 100 is
operating or is sold (i.e., irrespective of the impendence of
the headphones 105). Again, as is known to those skilled in
the art, the wireless device 100 has means for determining its
carrier and/or location and hence the government regulations
that may apply to set maximum signal levels and/or maximum
sound pressure levels. Thus, according to one embodiment, the
microprocessor 138 receives a signal indicative of the carrier
and/or location of the wireless device 100 and determines
whether a maximum signal level value and/or a maximum sound
pressure level value has been prescribed for the carrier
and/or location. The microprocessor 138 may do this by
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accessing a table 406 that stores wireless device carrier (or
location), corresponding headphones impedance values,
corresponding carrier specific maximum signal level values (if
any) for the audio amplifier 430, and/or corresponding carrier
specific maximum sound pressure level values (if any) for the
headphones 105. For example, the table 406 may indicate that
if the wireless device 100 is associated with a carrier based
in Great Britain, then the maximum sound pressure level should
be restricted to 100 dB (i.e., if the headphones 105 and
wireless device 100 are sold as a package). As another
example, the table 406 may indicate that if the wireless
device 100 is associated with a carrier based in Great
Britain, then the maximum sound pressure level should be
restricted to 94 dB (i.e., if the headphones 105 and wireless
device 100 are not sold as a package).
[0034]According to one embodiment, updates to the table 406
storing carrier (or wireless device location), corresponding
headphones impedance values, corresponding carrier specific
maximum signal level values (if any) for the audio amplifier
430, and corresponding carrier specific maximum sound pressure
level values (if any) for the headphones 105 may be
periodically downloaded to the wireless device 100 (e.g., over
the network 220).
[0035]According to one embodiment, the carrier associated with
the wireless device 100 may be determined from messages
delivered to the wireless device 100 over the network 220.
According to another embodiment, the carrier may be determined
from information stored in the wireless device's SIM card 162.
[0036] According to one embodiment, the location of the wireless
device 100 may be determined from messages delivered to the
wireless device 100 over the network 220. According to another
embodiment, the location of the wireless device 100 may be
determined by a global positioning system ("GPS") receiver
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(not shown) optionally provided for the device 100. According
to another embodiment, the location of the wireless device 100
may be determined from the location of antennae towers
associated with the network 220 on which the wireless device
100 operates.
[0037]FIG. 5 is a block diagram illustrating an alternate
headphones subsystem 400 in accordance with an embodiment of
the application. In FIG. 5, a signal source 510 (e.g.,
microprocessor 138) generates a signal (e.g., an audio signal,
an inaudible audio signal, etc.) that is applied to a digital
to analog converter ("DAC") 540. The output of the DAC 540 is
conditioned 530 (e.g., amplified 430, etc.) to allow for
impendence measurement 520 (e.g., via a resistor R, etc.) of
the headphones 105 connected to the headphones jack 506.
[0038]The application may provide several advantages. For
example, the method of the present application allows wireless
devices 100 to restrict maximum signal levels and maximum
sound pressure levels to prescribed legal limits when
necessary.
[0039] Aspects of the above described method may be illustrated
with the aid of a flowchart. FIG. 6 is a flow chart
illustrating operations 600 of modules 206 within the memory
200 of a wireless device 210 for controlling maximum signal
level output to headphones 105 of the wireless device 100, in
accordance with an embodiment of the application.
[0040]At step 601, the operations 600 start.
[0041]At step 602, an impedance Z of the headphones 105 is
determined.
[0042]At step 603, a carrier specific maximum signal level for
headphones having the impedance Z is determined.
[0043]At step 604, an audio amplifier 430 of the wireless
device 100 coupled to the headphones 105 is adjusted to
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restrict the maximum signal level output to the headphones 105
to the carrier specific maximum signal level.
[0044]At step 605, the operations 600 end.
[0045]The above described method is generally performed by the
wireless device 100. However, according to one embodiment, the
method can be performed by, or in combination with, a data
processing system (not shown) such a personal computer ("PC")
or server, a stereo system, a television system, etc.
[0046] While embodiments of this application are primarily
discussed as a method, a person of ordinary skill in the art
will understand that the apparatus discussed above with
reference to a wireless device 100 and a data processing
system, may be programmed to enable the practice of the method
of these embodiments. Moreover, an article of manufacture for
use with a wireless device 100 or data processing system, such
as a pre-recorded storage device or other similar computer
readable medium including program instructions recorded
thereon, may direct the wireless device 100 or data processing
system to facilitate the practice of the method of these
embodiments. It is understood that such apparatus and articles
of manufacture also come within the scope of the application.
[0047] The embodiments of the application described above are
intended to be exemplary only. Those skilled in this art will
understand that various modifications of detail may be made to
these embodiments, all of which come within the scope of the
application.
