She taught French in an elementary school in the London suburbs for a while, but then joined the University College Phonetics Department, headed by Daniel Jones.

She was the subeditor of the International Phonetic Association's journal Le Maître Phonétique for more than a decade, and was praised in her day for her teaching, both during the academic term and in the department's summer vacation courses.

[7] After graduating from Leeds, Armstrong taught French in East Ham for several years; she had success in this line of work, and was well on her way to becoming headmistress by the time she left this position in 1918.

[11] Those plans were temporarily put on hold when London County Council decided against a budgetary increase for the department in October, but in November 1917, Jones nominated Armstrong to receive a temporary, part-time lectureship, which she started in February 1918.

[21] Other positions she held at University College were Chairman of the Refectory Committee and Secretary of the Women Staff Common Room.

[42] In April 1927, she gave a lecture on English intonation to a meeting of the Modern Language Society [fi] of Helsinki, Finland.

[45] In the summer of 1934, Scottish phonetician J. C. Catford, then age 17, took a class in French phonetics taught by Armstrong and Hélène Coustenoble.

[46] Armstrong taught advanced phonetics to American linguist Lorenzo Dow Turner while he was doing postdoctoral research at the School of Oriental Studies from 1936 to 1937.

For instance, one year Le Maître Phonétique had specimens of Gã, Biscayan, Japanese English, Poitevin, and Punjabi.

[64] Armstrong's second specimen, published in 1929, was of Russian and consisted of a transcription of an excerpt of Nikolai Gogol's "May Night, or the Drowned Maiden".

[70] Her English Phonetic Reader included transcriptions of passages written by Alfred George Gardiner, Henry James, Robert Louis Stevenson, Thomas Hardy, and John Ruskin.

[73] One of the chief distinctions of "narrow transcription" for English was the use of the additional phonetic symbols for vowels, such as [ɪ] (as in the RP pronunciation of KIT), [ʊ] (FOOT), and [ɒ] (LOT).

[87] He also defended other transcription choices like using "sh" to represent an aspirated alveolar fricative as in the Burmese word ဆီ (IPA: [sʰì], "oil"), which Armstrong and Pe Maung Tin transcribed as "ˍshiː";[88] the reviewer thought it was confusing to use "sh" to refer to a sound other than the post-alveolar fricative represented by the English ⟨sh⟩ as in the word she (/ʃiː/).

[86] R. Grant Brown, a former member of the Indian Civil Service in Burma, praised A Burmese Phonetic Reader for being the joint work of a phonetician and a native speaker, writing "This excellent little book sets a standard which other writers on living Oriental languages will have to follow if they do not wish their work to be regarded as second-rate",[89] although he thought their transcription system was "too elaborate for ordinary use".

[92] British linguist Justin Watkins used Armstrong and Pe Maung Tin's translation of "The North Wind and the Sun" for his 2001 illustration of the IPA for Burmese in the Journal of the International Phonetic Association.

[108] Pike wrote that the work was "an influential contribution to the field";[100] in 1948, he described it as providing "the most widely-accepted analysis of British intonation".

[110] Pike wrote their tune-based intonation "proves insufficient to symbolize adequately (i.e. structurally) the intricate underlying system of contours in contrast one with another".

[112] Armstrong and Ward themselves wrote that they were aware there is "a greater wealth of detail than [is] here recorded", but that "attention has been concentrated on the simplest forms of intonation used in conversation and in the reading of narrative and descriptive prose" since the book's intended reader was a foreign learner of English.

[117] In the first chapter, she discusses techniques for French teachers to conduct ear-training exercises which were such an important part of her own teaching of phonetics.

[44] Farah's pronunciation had been the basis for Armstrong's 1933 specimen,[144] and he had also been the subject for a radiographic phonetic study conducted by UCL phonetician Stephen Jones.

[148] In 1981, American phonologist Larry Hyman called Armstrong's paper "pioneering"; she was the first to thoroughly examine tone or pitch in Somali.

[161] Australian British linguist Roy Clive Abraham wrote that he agreed with Armstrong on most parts regarding Somali phonetics: "there are very few points where I disagree with her".

He was employed by the Phonetics Department from 1935 to 1937 in order for Armstrong to carry out her research;[170] this was while Kenyatta was studying social anthropology at the London School of Economics under Bronisław Malinowski.

Daniel Jones entrusted Beatrice Honikman to write the remaining chapter and finalize the book's preparations for its 1940 publication; she was a lecturer at SOAS who had earlier done work on Kikuyu with Kenyatta, and she was also once Armstrong's student.

[174] She suggested that the voiced dental fricative [ð] be represented by ⟨d⟩ and the prenasalized plosive [ⁿd][f] by ⟨nd⟩; in parallel were the pairs [β][g] ⟨b⟩ / [ᵐb] ⟨mb⟩ and [ɣ] ⟨g⟩ / [ᵑg] ⟨ŋg⟩.

[182] Armstrong also proposed that the seven vowels of Kikuyu be represented by the IPA symbols ⟨i, e, ɛ, a, ɔ, o, u⟩;[183] this followed the practical orthography, now known as the Africa Alphabet, devised by the International Institute of African Languages and Cultures.

[202] University of Nairobi linguist Kevin C. Ford wrote that if Armstrong had not died before completing this book "there is no doubt she could have expanded her range of data and probably presented some rigorous analysis, which is sadly lacking in the published work".

[203] The South African linguist Clement Doke considered Armstrong's book to be "a model of meticulous investigation and recording", writing in 1945 that it should "serve as a model" for subsequent work on tone in Bantu languages,[204] and the American phonologist Nick Clements described it in a 1984 paper as "an extremely valuable source of information due to the comprehensiveness of its coverage and accuracy of the author's phonetic observations".

Boyanus was finally able to permanently move to England in January 1934, whereupon he became a lecturer in Russian and Phonetics at the School of Slavonic and East European Studies at the University of London.

[224][225][226] In early 1938, when her widower Simon Boyanus brought up the possibility of publishing Armstrong's Kikuyu manuscript, Daniel Jones arranged for Beatrice Honikman to see it through to publication.