Hello fellow Head-fiers!. This is my first review in Head-fi, but before I begin, I'd like to give a brief introduction about me. I'm an average individual who loves listening to almost wide range of music genres from classic to rock, except current pop, rap, and hip-hop, but I mainly listen to songs as long as they sound good! I primarily listen to metal and rock; but recently, I've gotten interested to Japanese's rock (J-rock) , and some J-pop. Besides, collecting earphones is also one of my recent hobbies thank to head-fi.org! Either good or bad, I keep them and I treat them with fatherly love. But I would like to share my thanks to Amazon.com for selling earphones cheaper than retail price and influential reviewers like lJokerl, Thebeatsguy, Earphonia, thatonenoob, ClieOs, and Mark2410 that have done organized and comprehensive writings (I wish I could write as good as them!); yet, their reviews help me choose best earphones that are worthy of my collection. You could see numbers of earphones I have under my profile and most of my favorite earphones are mainly derived from their reviews .
A lot of my friends and relatives thought my hobby is a weird one but I thought it's similar to having numbers of shoes or clothes that suit one's fashion style; yet, one wouldn't want to wear same shoe/clothes every day. It's fascinating to own variety of earphones because each of them has unique sound signature; yet, each has certain beauty and quality that can be appreciated. More importantly, they keep me out from getting bored of music because of listening solely just to one earphone and I need music to keep me through daily tasks. What interested me the most is that earphone technology has improved significantly since I begin my earphone hobby since 2012 and plenty of new earphones, successors, and competitors have emerged, so as an earphone enthusiast, I'd love to try 'em out! Yet, their release is beyond our grasp and has outpaced our knowledge of earphones, which is written in reviews. Somehow, many people are unsure about the performance of the new earphones and I believe most of them are eager to hear the reviews first before buying them. Therefore, I hope this article would be informative and serves as a reference of a certain earphone. If I made a mistake especially about technical quality like sound, please fix me up since I'm not sound analyst but casual listener! I also hope that I could learn and grow within Head-fi as well.
Introduction:
Before I discovered Head-fi, EPH-100 was one of my first earphones and I consider it as the best earphone I've had. I wrote my first-ever review in the amazon.com though I think it's more about my happy reaction than a proper review. Although I paid $150 ( now it's cheaper), EPH-100 gets full marks in all category: sound, spaciousness, comfort, isolation, and ease of use. Honestly, few of my collections could rival or none could have the sound that similar to the EPH-100. One earphone in mind is Carbo Basso which shares similar deep bass, satisfying mid, and spacious sound but the high could be somewhat gritty when played at high volume. Yet, its tonality is not as natural; yet, the comfort isn't as the same. Once I discovered head-fi, I found that most fellows agree that EPH-100 is one heck remarkable earphone. As earphone technology advancing in 2014, I was worried that Yamaha hadn't created any EPH-100 successors and many big companies like Westone, JVC, and Audio Technica have upgraded their arsenals.
By the end of 2014, my prayer had been answered as the new Yamaha EPH-M100 and M200 were released; however, they have an half-earbud shape that are completely different to their predecessor. The design appear to disfavor over-the-ear wearing as I love to; nonetheless, I still eager to try it out since I'm a Yamaha fanboy!. Yet there a was sale went on in the end of December '14 selling it for $100. It was $50 cheaper than its predecessor and for its successor, it's definitely a good news. I chose the EPH-M200 because they have the beta-titanium technology that allows the nozzle to flex so it is said it would conform with the ear canal for maximum comfort. Yet, this feature similar to the Gr07 mk.II featuring rotate-able nozzle to 360' degrees but the M200 is one of the few I know that follows this; yet, it's bendable so definitely good news!! During that time, there was not much published reviews about it in head-fi but only brief impressions; regardless, the purpose of this review is to determine whether EPH-M200 is an upgrade of EPH-100 or not. So I purchased.
The Package:
They arrived and they came in beautifully presented box instead of that rigid clamshell hard-to-be-opened plastic box of EPH-100, which is good so I can keep the box as part of my collections as well. They're far easier to open as well! I chose the black one because it's conservative, look professional, and won't look too flashy for public use.
Next, the Yammy is beautifully placed. Them earphones shine and luscious!
The accessories:
I like the hard-case of the M200s while the EPH-100's case is somewhat mushy. It also includes the quality check approval to proves that this unit is 100% functional and legitimate. It includes the ear tips ranging from XS, S, M(attached),L, and XL, just like the wide size of eartips of EPH-100, and a biggie plug connector which I don't use. Overall, the EPH-M200 provide similar idea of accessories like the 100s except the M200 includes that small quality check paper.
Build quality and look:
The physical look of earphones when taken out (sorry, forgot the 3.5mm connector) but it's 90' degree angled. It does have the half-earbud design so wearing over-the-ear is surely impossible. It appears it doesn't have stress relief as the cable just stick out from the housing without rubering; yet, they're made in shiny plastic and matte (on the grey part) but wish that It could've made from aluminum, just like that EPH-100.
Compared with the EPH-100, my Goodness,everything is humongous! The housing and the remote are bigger than housing of EPH-100, but it's light so it shouldn't be a problem. The cable is not supported with cable cinch; yet it doesn't have the memory characteristic of EPH-100. It is not as smooth as the 100s but somewhat stiffer and wavy. Least, it's not flat cable but has cylindrical type.
Lastly the fit.
Sadly, it can only be worn down due to half-earbud design and it can be microphonic. It is worsened by the huge and gaudy remote on the right side that tends to swing whenever I move or turn my head. Yet, it's not supported with a cable cinch to reduce microphonic so the only way to reduce the noise is by attaching earphone clipper or tug it inside the clothes. Besides, the comfort is hit-and-miss. It fits comfortably at first; but later on, the fit feels weird because the huge circular housing sits right in the external acoustic meatus (left image), a location surrounding the ear hole ; therefore, I tend to adjust the fit for every 15 minutes. Half of the times it inserts perfectly, but most of the times the fitting can be bothersome. I also note that the b-titanium tube isn't as flexible as advertised; to me, it's stiff and bends for about 0.1-0.3mm above the parallel line. Otherwise, It seals greatly but it doesn't isolate as much as the EPH-100 because the nozzle is shorter and the housing design prevents from getting deeper fit. Overall, I don't quite like the fit and I wish it could've been a straight barrel design instead, like the EPH-100, so less finicky fit.
Note:
During the course of listening, all of my observation is derived primarily from one source: Sansa Clip zip (non-rockboxed). I don't use any amps nor equalization at all as I prefer the natural sound of earphones in order to understand its beauty and strength. All my music files are 320kbps and some are FLAC files. I used the earphones in my daily tasks to see if it's bothersome or not. I also tested its isolation when at home, driving my car, and commuting for 1-2 hours. If one desire to know what songs / albums I listened with the M200, I'd be happily to list 'em.
The meat of review: sound.
Overall, the EPH-M200 has boosted, textured, and tactile bass, forwarded mid, overly smoothened treble , lack of sparkle, and intimate soundstage.
Bass
One aspect that struck me the most was obviously the bass: it's big, reaching deeper to sub-bass region and its bass is well-rendered. It doesn't bleed to the mid, in my opinion. Listening to recorded live music, like in rock/metal concert can be very exciting with these, as I find all my live albums are somewhat bass-shy and addition bass gives the fun and live factor. Any tracks that lack of bass depth can be improved with these. I like how the sound of bass guitar is emphasized in metal songs with these - it gives me the head-banging feeling! Its quantity is even more than the EPH-100 too, and I can safely say the M200 can be called the bass-head earphone. But, the bass can be tad over-dominating and boomy when listening to bass-heavy tracks. Yet, the bass is slow and not tight; listening to fast-beating technos, trance, or any metal tracks with rapid double-bass pedals can be fatiguing.
Treble
Aside of the impressive bass, the treble is very smooth, lacks of sparkle and never be sibilant. It differs where the EPH-100 has the sparkle that can be bit bothering when it comes to cymbal heavy or repetitively "tz-tz" tracks. This is good for treble-sensitive listeners like myself; however, the treble is overly smoothened, making overall sound dark and dull. Cymbals can be difficult to be heard and songs with lack of sparkle can be lifeless.
Mid
The mid also differs from EPH-100. While the 100s sounds thin and dry, the M200 sounds fuller and forward. However, instrumental sounds very thick and vocal sound can be nasal at some times. Yet, overall sound can be too shouty. Some songs can be too congested because of the boosted bass. Yet, I find that my ears are sensitive with forwarded mids; therefore, the mid often can be fatiguing. It's not because of my preference; typically, humans are sensitive to middle frequency 1, 2 and I was one them.
Soundstage
As the result of forwarded mid, the soundstage becomes intimate. Vocal definitely sounds centered right in the middle of one's head but its placement can be confusing. Somehow, the vocal sings from the right side but not the left side. For a bigger speaker, 15mm driver, implemented in the M200, it can be surprising that the soundstage can be so small. As the diameter of the driver gets bigger, the more spacious the soundstage should be expected, like comparing a headphone to an earphone. But, the head-room of this earphone is spherical and small; imagine all bands cramped inside your brain and the space is limited to the size of one's head. Yet, the 3D-ness is nearly non-existent because of the dull treble that lacks of sparkle. It doesn't have the transparency of EPH-100 but instead it sounds bloated and concentrated. This leads to obscurity in distinguish instrument location too: most of the times the bass-dominating side of earphone, like left side, can be louder than the right side. Often, the treble side which often come from right side can sound too quiet. Overall, I find the soundstage of M200 is its weakest point and disappointed that it doesn't retain the 3D-ness and spaciousness that its predecessor, EPH-100, has.
Lastly, I note that the earphone is easily driven. It plays really loud with only 1 to 1.5 volume bar under 'normal volume' setting in Sansa clip zip. So one needs to be careful when using these with non-sensitive volume bar like the Samsung S5, where the loud difference between bar is very big. I also note no hisses from my sansa as well. The earphones have been burned for about 2-3 days and I find no change with the sound. The bass did not mellowed out, the mid was still forwarded, and the soundstage still sound intimate and congested.
Conclusion:
Overall, EPH-M200 is a big-bass, thick-mid, and smooth-treble earphone but I'm disappointed with the dark, congested, and bloated sound signature combined the poor soundstage that lacks of space and proper spatial location, especially for the given price, $100 - it was on sale so the value would go back to the retail price in future. I could say M200 works as side-grade of EPH-100 as the M200 sounds nearly the opposite to EPH-100. But truthfully, M200 is more like a downgrade because it misses one important components of its predecessor: soundstage and 3D-ness. It is tuned toward youth generation and those who seek for bassier version of EPH-100 and if one find its treble can be bothersome, this can be a good choice. Its smoothened treble may apply to treble-sensitive listener too. However, it's hard to recommend these as the fit can be bothersome and its soundstage is too intimate; yet, 3D-ness is nearly non-existent. Lastly, the beta-titanium nozzle is too rigid and doesn't bend as much as the advertised. EPH-M200 can be impressive at first - like the bass and the smooth, fun sound factor - but it turns sour after long-term listening. I struggled to get used with the sound but my ears gave up because I cannot stand forwarded mid and intimate signature. I returned it back to Amazon.com in the following 14 days, making it the 1st earphone I've returned because it is fatiguing.
The overall impression and its comparison to EPH-100 are summarized in the following table:
Thanks for reading!
Reference:
1. Smith, Steven, W. Audio Processing. The Scientist and Engineer's Guide toDigital Signal Processing,. n.d. 2011. web. 17 Jan. 15. http://www.dspguide.com/ch22/1.htm
2. Erede, Steven. The Human Ear - Hearing, Sound Intensity and Loudness level. University of Illinois. 2014. web.17 Jan.2015.https://courses.physics.illinois.edu/phys406/lecture_notes/p406pom_lecture_notes/p406pom_lect5.pdf
A lot of my friends and relatives thought my hobby is a weird one but I thought it's similar to having numbers of shoes or clothes that suit one's fashion style; yet, one wouldn't want to wear same shoe/clothes every day. It's fascinating to own variety of earphones because each of them has unique sound signature; yet, each has certain beauty and quality that can be appreciated. More importantly, they keep me out from getting bored of music because of listening solely just to one earphone and I need music to keep me through daily tasks. What interested me the most is that earphone technology has improved significantly since I begin my earphone hobby since 2012 and plenty of new earphones, successors, and competitors have emerged, so as an earphone enthusiast, I'd love to try 'em out! Yet, their release is beyond our grasp and has outpaced our knowledge of earphones, which is written in reviews. Somehow, many people are unsure about the performance of the new earphones and I believe most of them are eager to hear the reviews first before buying them. Therefore, I hope this article would be informative and serves as a reference of a certain earphone. If I made a mistake especially about technical quality like sound, please fix me up since I'm not sound analyst but casual listener! I also hope that I could learn and grow within Head-fi as well.
Introduction:
Before I discovered Head-fi, EPH-100 was one of my first earphones and I consider it as the best earphone I've had. I wrote my first-ever review in the amazon.com though I think it's more about my happy reaction than a proper review. Although I paid $150 ( now it's cheaper), EPH-100 gets full marks in all category: sound, spaciousness, comfort, isolation, and ease of use. Honestly, few of my collections could rival or none could have the sound that similar to the EPH-100. One earphone in mind is Carbo Basso which shares similar deep bass, satisfying mid, and spacious sound but the high could be somewhat gritty when played at high volume. Yet, its tonality is not as natural; yet, the comfort isn't as the same. Once I discovered head-fi, I found that most fellows agree that EPH-100 is one heck remarkable earphone. As earphone technology advancing in 2014, I was worried that Yamaha hadn't created any EPH-100 successors and many big companies like Westone, JVC, and Audio Technica have upgraded their arsenals.
By the end of 2014, my prayer had been answered as the new Yamaha EPH-M100 and M200 were released; however, they have an half-earbud shape that are completely different to their predecessor. The design appear to disfavor over-the-ear wearing as I love to; nonetheless, I still eager to try it out since I'm a Yamaha fanboy!. Yet there a was sale went on in the end of December '14 selling it for $100. It was $50 cheaper than its predecessor and for its successor, it's definitely a good news. I chose the EPH-M200 because they have the beta-titanium technology that allows the nozzle to flex so it is said it would conform with the ear canal for maximum comfort. Yet, this feature similar to the Gr07 mk.II featuring rotate-able nozzle to 360' degrees but the M200 is one of the few I know that follows this; yet, it's bendable so definitely good news!! During that time, there was not much published reviews about it in head-fi but only brief impressions; regardless, the purpose of this review is to determine whether EPH-M200 is an upgrade of EPH-100 or not. So I purchased.
The Package:
They arrived and they came in beautifully presented box instead of that rigid clamshell hard-to-be-opened plastic box of EPH-100, which is good so I can keep the box as part of my collections as well. They're far easier to open as well! I chose the black one because it's conservative, look professional, and won't look too flashy for public use.
Next, the Yammy is beautifully placed. Them earphones shine and luscious!
The accessories:
I like the hard-case of the M200s while the EPH-100's case is somewhat mushy. It also includes the quality check approval to proves that this unit is 100% functional and legitimate. It includes the ear tips ranging from XS, S, M(attached),L, and XL, just like the wide size of eartips of EPH-100, and a biggie plug connector which I don't use. Overall, the EPH-M200 provide similar idea of accessories like the 100s except the M200 includes that small quality check paper.
Build quality and look:
The physical look of earphones when taken out (sorry, forgot the 3.5mm connector) but it's 90' degree angled. It does have the half-earbud design so wearing over-the-ear is surely impossible. It appears it doesn't have stress relief as the cable just stick out from the housing without rubering; yet, they're made in shiny plastic and matte (on the grey part) but wish that It could've made from aluminum, just like that EPH-100.
Compared with the EPH-100, my Goodness,everything is humongous! The housing and the remote are bigger than housing of EPH-100, but it's light so it shouldn't be a problem. The cable is not supported with cable cinch; yet it doesn't have the memory characteristic of EPH-100. It is not as smooth as the 100s but somewhat stiffer and wavy. Least, it's not flat cable but has cylindrical type.
Lastly the fit.
Sadly, it can only be worn down due to half-earbud design and it can be microphonic. It is worsened by the huge and gaudy remote on the right side that tends to swing whenever I move or turn my head. Yet, it's not supported with a cable cinch to reduce microphonic so the only way to reduce the noise is by attaching earphone clipper or tug it inside the clothes. Besides, the comfort is hit-and-miss. It fits comfortably at first; but later on, the fit feels weird because the huge circular housing sits right in the external acoustic meatus (left image), a location surrounding the ear hole ; therefore, I tend to adjust the fit for every 15 minutes. Half of the times it inserts perfectly, but most of the times the fitting can be bothersome. I also note that the b-titanium tube isn't as flexible as advertised; to me, it's stiff and bends for about 0.1-0.3mm above the parallel line. Otherwise, It seals greatly but it doesn't isolate as much as the EPH-100 because the nozzle is shorter and the housing design prevents from getting deeper fit. Overall, I don't quite like the fit and I wish it could've been a straight barrel design instead, like the EPH-100, so less finicky fit.
Note:
During the course of listening, all of my observation is derived primarily from one source: Sansa Clip zip (non-rockboxed). I don't use any amps nor equalization at all as I prefer the natural sound of earphones in order to understand its beauty and strength. All my music files are 320kbps and some are FLAC files. I used the earphones in my daily tasks to see if it's bothersome or not. I also tested its isolation when at home, driving my car, and commuting for 1-2 hours. If one desire to know what songs / albums I listened with the M200, I'd be happily to list 'em.
The meat of review: sound.
Overall, the EPH-M200 has boosted, textured, and tactile bass, forwarded mid, overly smoothened treble , lack of sparkle, and intimate soundstage.
Bass
One aspect that struck me the most was obviously the bass: it's big, reaching deeper to sub-bass region and its bass is well-rendered. It doesn't bleed to the mid, in my opinion. Listening to recorded live music, like in rock/metal concert can be very exciting with these, as I find all my live albums are somewhat bass-shy and addition bass gives the fun and live factor. Any tracks that lack of bass depth can be improved with these. I like how the sound of bass guitar is emphasized in metal songs with these - it gives me the head-banging feeling! Its quantity is even more than the EPH-100 too, and I can safely say the M200 can be called the bass-head earphone. But, the bass can be tad over-dominating and boomy when listening to bass-heavy tracks. Yet, the bass is slow and not tight; listening to fast-beating technos, trance, or any metal tracks with rapid double-bass pedals can be fatiguing.
Treble
Aside of the impressive bass, the treble is very smooth, lacks of sparkle and never be sibilant. It differs where the EPH-100 has the sparkle that can be bit bothering when it comes to cymbal heavy or repetitively "tz-tz" tracks. This is good for treble-sensitive listeners like myself; however, the treble is overly smoothened, making overall sound dark and dull. Cymbals can be difficult to be heard and songs with lack of sparkle can be lifeless.
Mid
The mid also differs from EPH-100. While the 100s sounds thin and dry, the M200 sounds fuller and forward. However, instrumental sounds very thick and vocal sound can be nasal at some times. Yet, overall sound can be too shouty. Some songs can be too congested because of the boosted bass. Yet, I find that my ears are sensitive with forwarded mids; therefore, the mid often can be fatiguing. It's not because of my preference; typically, humans are sensitive to middle frequency 1, 2 and I was one them.
Soundstage
As the result of forwarded mid, the soundstage becomes intimate. Vocal definitely sounds centered right in the middle of one's head but its placement can be confusing. Somehow, the vocal sings from the right side but not the left side. For a bigger speaker, 15mm driver, implemented in the M200, it can be surprising that the soundstage can be so small. As the diameter of the driver gets bigger, the more spacious the soundstage should be expected, like comparing a headphone to an earphone. But, the head-room of this earphone is spherical and small; imagine all bands cramped inside your brain and the space is limited to the size of one's head. Yet, the 3D-ness is nearly non-existent because of the dull treble that lacks of sparkle. It doesn't have the transparency of EPH-100 but instead it sounds bloated and concentrated. This leads to obscurity in distinguish instrument location too: most of the times the bass-dominating side of earphone, like left side, can be louder than the right side. Often, the treble side which often come from right side can sound too quiet. Overall, I find the soundstage of M200 is its weakest point and disappointed that it doesn't retain the 3D-ness and spaciousness that its predecessor, EPH-100, has.
Lastly, I note that the earphone is easily driven. It plays really loud with only 1 to 1.5 volume bar under 'normal volume' setting in Sansa clip zip. So one needs to be careful when using these with non-sensitive volume bar like the Samsung S5, where the loud difference between bar is very big. I also note no hisses from my sansa as well. The earphones have been burned for about 2-3 days and I find no change with the sound. The bass did not mellowed out, the mid was still forwarded, and the soundstage still sound intimate and congested.
Conclusion:
Overall, EPH-M200 is a big-bass, thick-mid, and smooth-treble earphone but I'm disappointed with the dark, congested, and bloated sound signature combined the poor soundstage that lacks of space and proper spatial location, especially for the given price, $100 - it was on sale so the value would go back to the retail price in future. I could say M200 works as side-grade of EPH-100 as the M200 sounds nearly the opposite to EPH-100. But truthfully, M200 is more like a downgrade because it misses one important components of its predecessor: soundstage and 3D-ness. It is tuned toward youth generation and those who seek for bassier version of EPH-100 and if one find its treble can be bothersome, this can be a good choice. Its smoothened treble may apply to treble-sensitive listener too. However, it's hard to recommend these as the fit can be bothersome and its soundstage is too intimate; yet, 3D-ness is nearly non-existent. Lastly, the beta-titanium nozzle is too rigid and doesn't bend as much as the advertised. EPH-M200 can be impressive at first - like the bass and the smooth, fun sound factor - but it turns sour after long-term listening. I struggled to get used with the sound but my ears gave up because I cannot stand forwarded mid and intimate signature. I returned it back to Amazon.com in the following 14 days, making it the 1st earphone I've returned because it is fatiguing.
The overall impression and its comparison to EPH-100 are summarized in the following table:
| | EPH-M200 | EPH-100 |
Loudness | Very. Gets loud at 1-1 .5 bar at normal volume | Average. Needs 3-4 bar to get sufficiently loud. |
Bass | Bigger bass, thunderous, tactile, very textured reaching to subbass. Midbass is boosted and tends to be boomy | Impactful and deep bass, but its quantity cannot reach to M200. |
Midrange | Forward and full. Vocal tends to get somewhat nasal and shouty. Instrument sounds very thick. | Thin, but it doesn't sound too recessed nor too forward. It's about right and clear. It can be little "drier" compared to M200. |
High | Overly smoothened. Lack of sparkle. Clear of sibilance. Cymbals can sound too dull and some tracks can be lifeless | Smooth but retain the sparkleness. It never be fatiguing nor sharp. Sibilance is non-existent. |
Soundstage | Very intimate. Vocals tend to get placed right in the center of one's head but can be confusing. 3D-ness or Instrument separation is poor and hard to distinguish. The side that produce bass, eg. Left side, tend to get louder and overwhelm the side producing treble, eg. right side. | Wide and has great 3D-ness thanks to the thin midrange and sparkleness. Instrument separation is very distinguishable. |
Comfort / fit | Lightweight but somewhat bothersome because the big housing sits deep in the external meatus. Tend to adjust the fit every 15 minutes during listening session. When insertion goes deep, it could be painful sometimes. | Lightweight and comfortable. The housing inserts right to the ear canal without being bothersome. It can be inserted deeply thanks to the straight-barrel design. Comfort is greatly improved by wearing over-the-ear. The shape and strain relief perpendicular to the housing allow for over-the-ear use. |
Non-fatigue level | 1 / 5 - Aside from the fit, the forwarded mid combined with the big bass fatigues my ears, which are sensitive to emphasized middle frequency. | 4 / 5 - Overall sound is smooth but the sparkle could be tiny-bit bothersome, especially in tracks with a lot of Tzs or repetitive cymbals. |
Isolation | 3 / 5 - Isolation is good. Still heard noise when I drive and crowd noise can be slightly heard in populated area. | 4 / 5 - Isolation is great, it can block some car noises and most people conversation. Can reduce vacuum cleaner noise by 70% |
Wearing style | Straight down only | Straight down and can be worn over-the ear ( preferred). |
Ease of use | Somewhat difficult; it gets uncomfortable if inserted too deeply and won't seal if too shallow. Spent time to get the optimal insertion depth. | Just plug in and voila! The straight barrel design makes it easier to insert. |
Microphonic | Can be microphonic and worsened by the huge remote that swings whenever I move. It doesn't have cable cinch to reduce the noise. having earphone clip or tug behind the clothes are must. | Microphonic when worn down but has cable cinch. Yet, wearing over-the-ear eliminates the noise. |
Thanks for reading!
Reference:
1. Smith, Steven, W. Audio Processing. The Scientist and Engineer's Guide toDigital Signal Processing,. n.d. 2011. web. 17 Jan. 15. http://www.dspguide.com/ch22/1.htm
2. Erede, Steven. The Human Ear - Hearing, Sound Intensity and Loudness level. University of Illinois. 2014. web.17 Jan.2015.https://courses.physics.illinois.edu/phys406/lecture_notes/p406pom_lecture_notes/p406pom_lect5.pdf
