DE102020005302A1 - Noise reduction with bone conduction speaker in headphones - Google Patents

Abstract

Technical problem of the invention = technical task and objective The comfortable use of headphones still depends on the acoustic environmental conditions during use. Usually, headphone users increase the volume of the device when the ambient noise level increases and thus also increase their own auditory stress. In order to counteract this increase in volume, noise suppression technologies (noise control) have already been developed. These technologies achieve a noticeable noise reduction. However, there is still a large proportion of background noise that cannot be reduced using this classic reduction of airborne noise. Solution to the problem or the technical task A significant increase can be expected if headphones are equipped with additional bone conduction loudspeakers. This reduces the background noise caused by the transmission of bone noise. The implementation is carried out by integrating one or more additional bone conduction loudspeakers (structure-borne sound transducers) in the headphones.Application exampleThe technology is suitable for integration in all current headphone designs:# in-ear headphones# on-ear headphones# over-ear headphones

Description

1 Introduction

This document describes a new noise suppression system for air conduction headphones with Active Noise Canceling (hereafter also called ANC). If this process is suitable, a corresponding patent application should be made and submitted.

The author and thus the inventor of this system are: Mr. Jakob Meer and Mr. Jürgen Meer.

2 State of the art

2.1 Initial situation

When using headphones in a noisy environment, most users consciously or unconsciously increase the volume of the playback device to drown out the background noise. This increases the auditory load for the wearer of the headphones and also for all other people who are in the immediate vicinity of the KH wearer. NC headphones reduce ambient noise so playback volume can remain at a lower level. This is the reason why the NC headphones are enjoying increasing popularity.

The noise canceling performance values achieved with the headphones on the market can be significantly increased by using additional technology. To increase these performance values, an additional bone conduction loudspeaker is integrated into the headphones.

2.2 Products available on the market

The first headphones with active suppression of external noise were developed and brought to market by the American manufacturer Bose in the 1980s. The first headphone products made with it were reserved exclusively for pilots or similarly important fields of application.

In the course of progressive improvements in technology and the associated production processes, these products could be manufactured more cheaply and thus also found their way into the so-called consumer market. In addition to the Bose company, there are now a dozen other manufacturers of this headphone technology.

• # In-Ear Kopfhörer
• # On-Ear Kopfhörer
• # Over-Ear Kopfhörer

There are currently 3 different designs for using ANC technology in headphones:

• # In ear headphones
• # On ear headphones
• # Over-ear headphones

The basic principle of noise cancellation is the same for all headphone variants mentioned above. The ambient noise is recorded by one or more built-in microphones. The headphones' built-in DSP (DSP=Digital Signal Processing) shifts the phase of the low frequencies by 180°. As a result, the ambient noise is almost eliminated and the wearer of the device hardly notices it during acoustic playback via the air line loudspeaker (also referred to below as LLL). The greatest noise suppression effect is currently achieved with the so-called over-ear headphones. The good suppression values achieved in this way can be attributed to the structural designs and optimizations that are possible with this design. For example, more material can be used for passive insulation in this type of headphone.

Due to the physical and human anatomical conditions, there is still a way to significantly improve the noise suppression.

3 Patent Description

The improvement outlined in the previous chapters is achieved by integrating a pure bone conduction loudspeaker (also referred to below as KLL) in the technical, constructive system concept of the over-ear headphones.

These bone conduction headphones are currently not available with ANC technology. The main area of application for these loudspeakers is in the area of water sports. The basic principle of KLL is based on the use of a closed bone sound transducer. This transmits the sound via vibration to the petrous bone (petrous bone = skull bone directly behind the human ear). The sound thus reaches the inner ear directly.

3.1 Initial physical and anatomical situation

• # Kanal 1: Übertragung durch Luftschall
• # Kanal 2: Übertragung durch Knochenschall

Anatomically, external noise (i.e. outside the human body) is transmitted to the ear via two channels:

• # Channel 1: Airborne transmission
• # Channel 2: transmission by bone conduction

From levels beyond 50dB hearing level (hearing level = hearing threshold) (in the following also called HL) the sounds are no longer picked up exclusively via the airborne sound connection path eardrum-middle ear-inner ear. At these volume levels, the sound always begins to be transmitted via the cranial bones. This so-called bone sound is transmitted via the connection between the petrous bone and the inner ear. The transmission effect of the second channel sets a natural, physical limit to the suppression effect of the ANC headphones.

This is where the solution described in this patent comes into play. The previously known ANC noise suppression process has been supplemented with a bone sound-based process.

With this method, a signal that is also in phase opposition (anti-sound) is played back in parallel to the ANC via the bone conduction loudspeaker. The KLL is integrated in the rear or front area of the ear-enclosing loudspeaker capsule of the headphones at the level of the padded ear contact surface. It is important that the KLL has direct contact with the cranial bone in the area of the petrous bone or cheekbone.

3.2 Results of the solution concept

1. 1. Antischall kommt klassisch über die Integrierten LLL und zusätzlich über den KLL. Dieser Modus ist für die maximal mögliche Unterdrückung der Umgebungsgeräusche ausgelegt.
2. 2. Antischall kommt ausschließlich über den KLL. Dieser Modus ist für die bestmögliche Klangqualität bei aktivierter ANC Funktion gedacht.

It is planned that the headphone can be operated via 2 modes:

1. 1. Anti-noise comes classically via the integrated LLL and additionally via the KLL. This mode is designed for the maximum possible suppression of ambient noise.
2. 2. Anti-noise comes exclusively via the KLL. This mode is intended for the best possible sound quality with the ANC function activated.

The two operating modes lead to the following results:

Operation in mode 1:

This mode means that the noise reduction values that can be achieved with the classic ANC method are significantly increased. This increase is due to the suppression of background noise during bone conduction transmission. The mode is recommended when a headphone user moves in an environment with loud, external noise, such as traveling by car, train or plane.

Operation in mode 2:

This mode leads to an improvement in the audio signals transmitted with the LLL, such as music, speech, etc., in normal external noise scenarios. The additional KLL relieves the LLL of the transmission of the anti-noise or ANC signal. This makes the LLL's audio signal clearer and more dynamic despite the ANC function being activated. The characteristic background noise of conventional over-ear headphones with ANC functionality is also significantly reduced. This mode is recommended for audiophile applications, such as uninterrupted music enjoyment at home or as active hearing protection for orchestra musicians.

Claims (8)

General integration of a KLL in a headphone (regardless of whether this basic device is equipped with or without ANC technology). System for reducing external noise in headphones by supplementing the well-known Active Noise Canceling technology with a bone conduction speaker for noise reduction using the principle of destructive interference. integration of the system claim 2 in the technological and structural design concept of the common over-ear headphones. In addition, integration of the system after claim 2 into the technological and structural concept of all other possible headphone designs. The name of the system after claim 2 is Enhanced Active Noise Canceling (alternatively Extended Active Noise Cancelling), abbreviated to EANC. The system after claim 1 until 5 is characterized in that - with the exception of bone conduction loudspeakers - an additional bone conduction loudspeaker is built into an existing headphone. This bone conduction loudspeaker lies directly on the so-called petrous bone and on the temporal bone of the human cranial bone. The system after claim 1 until 6 is characterized in that a separate ANC signal is generated in the control electronics for the bone conduction loudspeaker. This signal control can either be integrated into the already existing ANC signal control for the air duct loudspeaker or be generated and provided by a separate control module. The system after claim 1 until 7 is characterized in that bone conduction speakers in the control electronics an ANC signal is generated at all. This signal control can either be integrated into the already existing signal control for the bone conduction loudspeaker or be generated and provided by a separate control module.