Oticon Agil. Connectivity Matters - A Whitepaper. Agil Improves ConnectLine Sound Quality

Transcription

1 Oticon Agil Connectivity Matters - A Whitepaper Agil Improves ConnectLine Sound Quality

2 M. Lisa Sjolander, AuD Oticon A/S, Smørum, Denmark Agil Improves ConnectLine Sound Quality Wireless technology is part of our lives from the garage door opener, FM or satellite radio in the car, Bluetooth headsets, cell phones, lap top computers and hearing instruments. The increased availability of wireless technology in external audio devices and new wireless technology in hearing instruments allows hearing instrument users to connect to an ever increasing number of audio devices. For several years a team of engineers and audiologists at Oticon has focused on improving several common listening situations using wireless technology. This led to development of the Connect- Line; ConnectLine is a family of devices: the Oticon Streamer, TV Adapter and Phone Adapter that allow Oticon hearing instruments to wirelessly connect to up to eight external audio devices. ConnectLine is an integrated system, which unique because it allows flexible switching between devices with the push of a button. For example, if a person is watching TV using ConnectLine and a phone call comes in the listener accepts the call by simply pressing the phone button on the Streamer. When the call is over the TV program streaming will resume. ConnectLine provides benefit to hearing impaired people by providing hassle free listening to external audio devices and improving speech understanding. Speech understanding is improved by sending the signal to both ears and providing appropriate ear specific amplification through the hearing instruments. Also, sending the signal directly from the sound source to the hearing instruments, without the interference of background noise, improves the signal to noise ratio and the sound quality. Lab tests showed significant improvements in speech understanding using ConnectLine and hearing instruments versus hearing instruments alone 1. Field studies using the ConnectLine have shown fast acceptance of ConnectLine and self perceived benefit 2. This paper concentrates on improvements to sound quality for streaming with Oticon s Agil hearing instruments and ConnectLine. The improvements to sound quality are integrated in the Agil hearing instrument; ConnectLine has the same easy to use functionality as before, just with better sound quality. Two new algorithms, Power Bass and Widening, were developed to enhance sound quality with Agil hearing instruments and ConnectLine; together these features are called Connect[+]. Agil and ConnectLine continue to provide easy to use connectivity to external audio devices and to improve speech understanding. Improvements to sound quality are motivated by listeners need for excellent sound quality in all listening situations. In fact, sound quality and signal processing were rated the most important factors for hearing instrument consumers satisfaction in Marketrak VIII 3. Sound quality for streaming was improved by focusing on the unique problems that occur when streaming namely a lack of low frequencies and unnatural, in the head, sound experience. These problems only occur when streaming sound, so the new algorithms were developed specifically for improving streamed listening. Power Bass Generally, when listening with hearing instruments, sound is received both from the hearing instrument receiver and through the vent, giving a balanced full sound quality. The more open the vent is the more sound, particularly low frequency sound, is able to enter and leave the ear through the vent. Allowing low frequency sound to leave the ear through the vent reduces problems with occlusion when talking and chewing, which is a really good thing. But when listening to streamed audio, sound enters the ear only via the hearing instrument receiver so less low frequency sound enters the ear and more escapes from the ear. When streaming the lack of low fre- 2 3

3 quencies can result in a thin or tinny sound quality separate tones because the brain combines the har- Widening preference for listening to music, music with speech particularly for open fittings. To solve this problem monics with the fundamental. This gives the percep- Another aspect of sound that is different when and speech with Widening on versus listening the Power Bass algorithm was developed; Power tion of a louder richer sounding fundamental. When streaming is that the sound seems to originate in the without Widening. The results for all stimuli Bass enhances low frequency sound, providing fuller streaming the input signal is continuously monitored head rather than in the surroundings- as one nor- and settings are shown in figure 3. Participants re- and richer sound quality when streaming. to allow the selection of the appropriate bass boost mally experiences. The location of a sound source ported that the sound was more pleasant and that it and harmonics. This gives an optimal bass sound. can generally be identified quite accurately based had a more open and airy sound quality with Power Bass uses a dual scheme to enhance the per- on the differences between ears in level, phase and Widening than without 5. The results and participants ception of bass. Low frequencies are increased as The preferences for Power Bass settings were test- pinna cues. For streamed audio these cues are miss- reports show that Widening improves the per- much as possible, and harmonics are added to en- ed on ten people with mild to moderate hearing loss- ing, which gives the perception that the sounds are ception of space and sound quality when streaming. hance the perception of bass. For soft input signals es using open fit hearing instruments. Testing was originating inside the head. This is fine for listening the low frequencies are simply increased and no har- conducted using a paired comparison test where to speech, however, for music listening this can be Preference for Widening monics are added. For louder input signals the ability participants were blind to the conditions. Speech, perceived as being unnatural and boring. 1 off to turn up the low frequency signal is limited due to the lack of head room, so harmonics of the low frequency part of the signal are added to enhance the low frequency sound. Adding harmonics of the fundamental, also known as overtones, creates a fuller and richer sound because the brain fills in the missing fundamental when the harmonics are present. A visual representation of the creation of harmonics of a 15 Hz tone is shown in figure 1. This example shows that when shown visually the addition of harmonics speech with background music and music alone were tested with various levels of Power Bass. Test results showed that participants preferred Power Bass on and there was a significant preference for the maximum Power Bass setting for all stimuli tested. Results for all stimuli tested are shown in figure 2 4. These findings show that Power Bass significantly improves the sound quality for streaming with open fittings. Widening is an algorithm that changes the acoustic cues when streaming to give the perception of a natural sound, as opposed to a sound that is in the head. The virtual cues are created based on how sound is modified when listening in a real room. When music is played in a room the music usually first reaches the listener directly from the speaker, then as the sound is reflected off the walls, it reaches the listener again. Generally, the delay between the di- % of trials setting was preferred Jazz Classical Speech + music Speech Overall low/min mid high/max Level in db is obvious, however, when we are listening the only difference we can perceive is that the 15 Hz sounds louder. We do not hear the addition of harmonics as PowerBass ON PowerBass OFF % of trials setting was preferred Preference for PowerBass Settings Jazz Classical Speech + Speech Overall off low/min mid high/max rect and reflected sound is so short that the sounds are combined in our mind and we only perceive one sound; an echo is heard if the delay between direct and reflected sound is very long. Each reflection that enters the ear introduces new level and timing differences between the ears. The differences between the right and left ear are what give us the impression of an external sound with a certain direction played in a certain type of room. These reflections also make music sound richer and fuller. Widening creates the impression that music is being played in a living room by generating the appropriate Figure 3: Shows preferred level for Widening for the 11 participants. Overall results show a significant preference for Widening (p<.5). If all stimuli had been equally preferred the ratings for all four settings would be around 25%. Field Test Results with Agil and ConnectLine Lab test results with hearing impaired listeners showed that Power Bass and Widening improved sound quality by adding bass and space to the listening experience. After having found settings for Power Bass and Widening, which Frequency (Hz) Figure 1: Addition of harmonics to a 15 Hz pure tone. In the visual representation the fundamental tone looks very different with the addition of harmonics, but the only difference in the auditory perception is that adding harmonics makes the fundamental sound louder. Figure 2: Shows preferred level of Power Bass for the 1 participants using open fit hearing instruments. Overall results show a significant preference for Power Bass- (p<.5). If all stimuli had been equally preferred the ratings for all four settings would be around 25%. virtual cues. Widening was tested on eleven hearing impaired people with mild to severe hearing losses. Participants made paired comparisons of four different settings for Widening: off, low, mid and high. The high setting had the longest reverberation time, i.e. the longest time between first stimulus and the virtual reflection. Testing with hearing impaired listeners showed that participants had a significant improved the listening experience when streaming we decided to test Agil Pro with ConnectLine in the field to find out how it worked for people in their day to day lives and how they rated the sound quality. Testing hearing instrument settings in a realistic environment is important because preferences in a highly controlled lab setting can differ greatly from preferences in the real world. 4 5

4 Experienced hearing instrument users with mild to figure 4. Also, the sound quality for streamed music severe hearing losses were recruited for testing. listening was evaluated in the field test; participants Participants were fit with Agil. The following styles rated the bass, treble and overall volume for music were tested: ITE, ITC, minirite, Rite and BTE. Par- listening. Participants indicated that the settings ticipants tested one or several ConnectLine devices were just right 2. These results show that the default depending on their needs. (This is why the number of settings provide agreeable sound quality for music participants who tested the TV Adapter, Cell Phone and Landline Phone Adapter are different, see figure 5 for exact numbers for each condition.) Test settings for Power Bass and Widening were selected Sound Quality Ratings for Streamed based on the overall preferences in Power Bass and Widening lab tests, all other settings were Volume the default settings in Genie. Participants wore Agil hearing instruments and used ConnectLine for 2-4 Treble weeks. During the field testing participants filled out Bass questionnaires evaluating their perception of sound quality and benefit with Agil and ConnectLine too little just right too much Results from the field test show that experienced listening, ratings are shown in figure 5. hearing instrument users received significant ben- Figure 5: Sound quality ratings when listening to music efit using ConnectLine and Agil hearing instruments for listening to cell phone, landline phone and TV 2. with Agil and ConnectLine. Rated by 11 hearing impaired people with mild to severe hearing losses. Preference ratings show an overwhelming preference for Agil with ConnectLine versus their own Field and lab test results show that Agil with Con- solution (hearing instrument alone or hearing in- nectline, Power Bass and Widening, provides strument and t-coil); Field test results are shown in excellent sound quality for streaming. ConnectLine has the potential to benefit many hearing impaired % of participants Field Test Results Agil Connect+ better No preference Own solution better people. As a matter of fact, ConnectLine can improve speech understanding in three of the six most important listening situations: landline phone, television and cell phone listening, reported in the most recent Marketrak 3. We need to stop underestimating hearing impaired peoples, particularly elderly hearing impaired peoples, need for connectivity and begin giving them the best listening access possible. References 2 1 TV (N=17) Cell Phone (N=12) Landline Phone (N=11) 1 Sjolander M. L., Bergmann, M., & Hansen L. B. Improving TV listening for hearing aid users. Hearing Review. 29;16(11): Minnaar, P. New Algorithm designed to enhance low frequencies in open-fit hearing aids. Hearing Journal. 21; 63 (3): 4,42-44 Figure 4: Results from a field test with Agil and ConnectLine. Participants compared their listening satisfaction with Agil and Connectline to listening solution they previously used. Significantly more participants were satisfied with Con- 2 Hansen, L. B. & Holmberg, M. 21. Oticon Agil Connect[+] Product test results. Oticon A/S, Copenhagen, Denmark, (unpublished data). 5 Minnaar, P. Enhancing music with virtual sound sources. Submitted to Hearing Journal. nectline and Agil than their own listening solutions. 3 Kochkin, S. MarkeTrak VIII: Consumer satisfaction with hearing aids is slowly increasing.21; 63(1): 19, 2, 22, 24, 26,

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